Liquid-crystal display

ABSTRACT

Disclosed are liquid-crystal (LC) media for use in LC displays of the PS (polymer stabilised) or PSA (polymer sustained alignment) type which contain a liquid-crystal (LC) mixture that contains one or more compounds of formula I

The present invention relates to liquid-crystal (LC) media for use in LCdisplays of the PS (polymer-stabilised) or PSA (polymer-sustainedalignment) type.

The liquid-crystal displays (LC displays) used at present are usuallythose of the TN (twisted nematic) type. However, these have thedisadvantage of a strong viewing-angle dependence of the contrast. Inaddition, so-called VA (vertical alignment) displays are known whichhave a broader viewing angle. The LC cell of a VA display contains alayer of an LC medium between two transparent electrodes, where the LCmedium usually has a negative value of the dielectric (DC) anisotropy.In the switched-off state, the molecules of the LC layer are alignedperpendicular to the electrode surfaces (homeotropically) or have atilted homeotropic alignment. On application of an electrical voltage tothe electrodes, a realignment of the LC molecules parallel to theelectrode surfaces takes place. Furthermore, OCB (optically compensatedbend) displays are known which are based on a birefringence effect andhave an LC layer with a so-called “bend” alignment and usually positive(DC) anisotropy. On application of an electrical voltage, a realignmentof the LC molecules perpendicular to the electrode surfaces takes place.In addition, OCB displays normally contain one or more birefringentoptical retardation films in order to prevent undesired transparency tolight of the bend cell in the dark state. OCB displays have a broaderviewing angle and shorter response times compared with TN displays. Alsoknown are IPS (In-plane switching) displays, which contain an LC layerbetween two substrates, only one of which has an electrode layer,usually with a comb-shaped structure. On application of a voltage, anelectric field which has a significant component parallel to the LClayer is thereby generated. This causes a realignment of the LCmolecules in the layer plane. Furthermore, so-called FFS (fringe-fieldswitching) displays have been proposed (see, inter alia, S. H. Jung etal., Jpn. J. Appl. Phys., Volume 43, No. 3, 2004, 1028), which likewisecontain two electrodes on the same substrate, but, in contrast to IPSdisplays, only one of these is in the form of a structured (comb-shaped)electrode, and the other electrode is unstructured. A strong, so-called“fringe field” is thereby generated, i.e. a strong electric field closeto the edge of the electrodes, and, throughout the cell, an electricfield which has both a strong vertical component and also a stronghorizontal component. Both IPS displays and also FFS displays have a lowviewing-angle dependence of the contrast.

In VA displays of the more recent type, uniform alignment of the LCmolecules is restricted to a plurality of relatively small domainswithin the LC cell. Disclinations may exist between these domains, alsoknown as tilt domains. VA displays having tilt domains have, comparedwith conventional VA displays, a greater viewing-angle independence ofthe contrast and the grey shades. In addition, displays of this type aresimpler to produce since additional treatment of the electrode surfacefor uniform alignment of the molecules in the switched-on state, suchas, for example, by rubbing, is no longer necessary. Instead, thepreferential direction of the tilt or pretilt angle is controlled by aspecial design of the electrodes. In so-called MVA (multidomain verticalalignment) displays, this is usually achieved by the electrodes havingprotrusions which cause a local pretilt. As a consequence, the LCmolecules are aligned parallel to the electrode surfaces in differentdirections in different, defined regions of the cell on application of avoltage. “Controlled” switching is thereby achieved, and the formationof interfering disclination lines is prevented. Although thisarrangement improves the viewing angle of the display, it results,however, in a reduction in its transparency to light. A furtherdevelopment of MVA uses protrusions on only one electrode side, whilethe opposite electrode has slits, which improves the transparency tolight. The slitted electrodes generate an inhomogeneous electric fieldin the LC cell on application of a voltage, meaning that controlledswitching is still achieved. For further improvement of the transparencyto light, the separations between the slits and protrusions can beincreased, but this in turn results in a lengthening of the responsetimes. In the so-called PVA (patterned VA), protrusions are renderedcompletely superfluous in that both electrodes are structured by meansof slits on the opposite sides, which results in increased contrast andimproved transparency to light, but is technologically difficult andmakes the display more sensitive to mechanical influences (tapping,etc.). For many applications, such as, for example, monitors andespecially TV screens, however, a shortening of the response times andan improvement in the contrast and luminance (transmission) of thedisplay are demanded.

A further development are the so-called PS (polymer-stabilised)displays, which are also known under the term “PSA” (polymer-sustainedalignment). In these, a small amount (for example 0.3%, typically <1%)of a polymerisable compound is added to the LC medium and, afterintroduction into the LC cell, is polymerised or crosslinked in situ,usually by UV photopolymerisation, with an electrical voltage appliedbetween the electrodes. The addition of polymerisable mesogenic orliquid-crystalline compounds, also known as “reactive mesogens” (RMs),to the LC mixture has proven particularly suitable.

In the meantime, the PSA principle is being used in diverse classical LCdisplays. Thus, for example, PSA-VA, PSA-OCB, PS-IPS/FFS and PS-TNdisplays are known. The polymerisation of the polymerisable compound(s)preferably takes place with an applied electrical voltage in the case ofPSA-VA and PSA-OCB displays, with or without, preferably without, anapplied electrical voltage in the case of PSA-IPS displays. As can bedemonstrated in test cells, the PSA method results in a pretilt in thecell. In the case of PSA-OCB displays, it is therefore possible for thebend structure to be stabilised so that an offset voltage is unnecessaryor can be reduced. In the case of PSA-VA displays, this pretilt has apositive effect on response times. For PSA-VA displays, a standard MVAor PVA pixel and electrode layout can be used. In addition, however, itis possible, for example, to manage with only one structured electrodeside and no protrusions, which significantly simplifies production andat the same time results in very good contrast at the same time as verygood transparency to light. PSA-VA displays are described, for example,in JP 10-036847 A, EP 1 170 626 A2, EP 1 378 557 A1, EP 1 498 468 A1, US2004/0191428 A1, US 2006/0066793 A1 and US 2006/0103804 A1. PSA-OCBdisplays are described, for example, in T.-J-Chen et al., Jpn. J. Appl.Phys. 45, 2006, 2702-2704 and S. H. Kim, L.-C-Chien, Jpn. J. Appl. Phys.43, 2004, 7643-7647. PS-IPS displays are described, for example, in U.S.Pat. No. 6,177,972 and Appl. Phys. Lett. 1999, 75(21), 3264. PS-TNdisplays are described, for example, in Optics Express 2004, 12(7),1221.

Like the conventional LC displays described above, PSA displays can beoperated as active-matrix or passive-matrix displays. In the case ofactive-matrix displays, individual pixels are usually addressed throughintegrated, non-linear active elements, such as, for example,transistors (for example thin-film transistors, “TFTs”), and in the caseof passive-matrix displays, they are usually addressed by the multiplexmethod, as known from the prior art.

In particular for monitor and especially TV applications, optimisationof the response times, but also of the contrast and luminance (thus alsotransmission) of the LC display continues to be demanded. The PSA methodcan provide crucial advantages here. In particular in the case ofPSA-VA, a shortening of the response times, which correlates with ameasurable pretilt in test cells, can be achieved without significantadverse effects on other parameters.

However, it has been found that the LC mixtures and RMs known from theprior art still have some disadvantages on use in PSA displays. Thus,not every desired soluble RM by far is suitable for use in PSA displays,and it is often difficult to find more suitable selection criteria thanthe direct PSA experiment with pretilt measurement. The choice becomeseven smaller if polymerisation by means of UV light without the additionof photoinitiators is desired, which may be advantageous for certainapplications. In addition, the LC mixture (also referred to as “LC hostmixture” below)+polymerisable component “material system” selectedshould have the lowest possible rotational viscosity and the bestpossible electrical properties, with the emphasis here being on theso-called “voltage holding ratio” (VHR or HR). In connection with PSAdisplays, a high VHR after irradiation with UV light is, in particular,of central importance since UV exposure is a necessary part of thedisplay production process, but naturally also occurs as “normal”exposure in the finished display.

However, the problem arises that not all LC mixture+polymerisablecomponent combinations by far are suitable for PSA displays since, forexample, no tilt or an inadequate tilt arises or since, for example, theVHR is inadequate for TFT display applications.

In particular, it would be desirable to have available novel materialsfor PSA displays which generate a particularly low pretilt angle.Materials which generate a lower pretilt angle during polymerisation forthe same exposure time than the materials known to date, and/or throughthe use of which the (higher) pretilt angle that can be achieved usingthe known materials can already be achieved after a shorter exposuretime would be particularly desirable. The production time (tact time) ofthe display could thus be shortened and the costs of the productionprocess reduced. A faster polymerisation rate of the RM is alsoparticularly advantageous in order, if appropriate, to enable residualamounts of unpolymerised RMs still present to react as quickly aspossible after the tilt angle has been established. The presence ofunreacted RMs in the display may have a disadvantageous effect on thedisplay properties. Besides fast polymerisation of the RMs, the mostcomplete polymerisation possible of the RMs is therefore also desirable.

There is thus still a great demand for PSA displays, in particular ofthe VA and OCB type, and for LC media and polymerisable compounds foruse in such displays, which do not have the disadvantages describedabove or only do so to a small extent and have improved properties. Inparticular, there is a great demand for PSA displays, and for materialsfor use in PSA displays, which facilitate a high specific resistance atthe same time as a large working-temperature range, short responsetimes, even at low temperatures, and a low threshold voltage, a lowpretilt angle, a multiplicity of grey shades, high contrast and a broadviewing angle, and have high values of the voltage holding ratio (VHR)after UV exposure.

The invention has the object of providing novel LC media for use in PSAdisplays which do not have the disadvantages indicated above or only doso to a reduced extent, enable a low pretilt angle to be established,and preferably at the same time facilitate very high specific resistancevalues, high VHR values, low threshold voltages and short responsetimes.

This object has been achieved in accordance with the invention by LCmedia and LC displays as described in the present application. Inparticular, It has been found, surprisingly, that the use of LC mediaaccording to the invention in PSA displays facilitates particularly lowpretilt angles and fast establishment of the desired tilt angles. Thishas been demonstrated in connection with an LC medium by means ofpretilt measurements. In particular, a pretilt has been achieved withoutthe addition of photoinitiator. In addition, the materials according tothe invention exhibit significantly faster generation of the pretiltangle compared with the materials known from the prior art, as has beendemonstrated by exposure time-dependent measurements of the pretiltangle. In addition, it has been found that, on use of LC media accordingto the invention, both the rate and completeness of the polymerisationof the RMs can be significantly increased compared with the LC mediaknown from the prior art. This enables both a shortening of the exposuretime and thus more efficient and economic performance of the process,and a reduction in the residual amount of undesired, unpolymerised RMsin the display.

The invention relates to the use of LC mixtures comprising one or morecompounds of the formula I

in which the individual radicals have the following meanings:

-   R¹ and R² each, independently of one another, denote alkyl having 1    to 12 C atoms, where, in addition, one or two non-adjacent CH₂    groups may be replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such    a way that O atoms are not linked directly to one another,    preferably alkyl or alkoxy having 1 to 6 C atoms,-   A¹, A², A³, A⁴ each, independently of one another, denote

-   one, two or three of the radicals A¹, A², A³ and A⁴ also denote

-   L¹ and L² each, independently of one another, denote H, F, Cl, OCF₃,    CF₃, CH₂F, CHF₂,-   Z¹, Z², Z³ each, independently of one another, denote —COO—, —OCO—,    —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —SCH₂—, —CH₂S—, —CH₂CH₂—, —C₂F₄—,    —CH₂—CF₂—, —CF₂CH₂—, —(CH₂)₂—, —CH═CH—, —CF═CF—, —CH═CF—, —CF═CH—,    —C≡C—, —CH═CHCH₂O—, or a single bond, where, in the case where m=0,    Z¹ and Z² do not simultaneously denote a single bond,-   z denotes 3, 4, 5 or 6,-   m denotes 0 or 1,    in LC displays of the PS (polymer stabilised) or PSA (polymer    sustained alignment) type.

The invention furthermore relates to an LC medium comprising an LCmixture according to the invention as described above and below, and oneor more polymerisable compounds, preferably selected from the groupconsisting of reactive mesogens.

The invention furthermore relates to an LC medium comprising an LCmixture according to the invention as described above and below, and apolymer obtainable by polymerisation of one or more polymerisablecompounds, which are preferably selected from the group consisting ofreactive mesogens.

The invention furthermore relates to an LC medium comprising

-   -   a polymerisable component A) comprising one or more        polymerisable compounds, preferably selected from reactive        mesogens, and    -   a liquid-crystalline component B), also referred to as “LC host        mixture” below, consisting of an LC mixture according to the        invention comprising one or more compounds of the formula I as        described above and below.

The invention furthermore relates to an LC medium comprising

-   -   a polymer obtainable by polymerisation of a polymerisable        component A) comprising one or more polymerisable compounds,        preferably selected from reactive mesogens, and    -   a liquid-crystalline component B), also referred to as “LC host        mixture” below, consisting of an LC mixture according to the        invention comprising one or more compounds of the formula I as        described above and below.

The invention furthermore relates to the use of LC mixtures and LC mediaaccording to the invention in PS and PSA displays, in particular the usein PS and PSA displays containing an LC medium, for generating a tiltangle in the LC medium by in-situ polymerisation of the polymerisablecompound(s) in the PSA display with application of an electric ormagnetic field.

The invention furthermore relates to an LC display containing an LCmedium according to the invention, in particular a PS or PSA display,particularly preferably a PSA-VA, PS-IPS or PS-FFS display.

The invention furthermore relates to an LC display of the PS or PSA typecontaining an LC cell consisting of two substrates, where at least onesubstrate is transparent to light and at least one substrate has anelectrode layer, and a layer, located between the substrates, of an LCmedium comprising a polymerised component and a low-molecular-weightcomponent, where the polymerised component is obtainable bypolymerisation of one or more polymerisable compounds in the LC mediumbetween the substrates of the LC cell with application of an electricalvoltage, and where the low-molecular-weight component is an LC mixtureaccording to the invention as described above and below.

The invention furthermore relates to a process for the preparation of anLC medium according to the invention by mixing one or morelow-molecular-weight liquid-crystalline compounds, or an LC mixtureaccording to the invention, with one or more polymerisable compounds,and optionally with further liquid-crystalline compounds and/oradditives.

The invention furthermore relates to a process for the production of anLC display according to the invention by mixing an LC mixture accordingto the invention with one or more polymerisable compounds and optionallywith further liquid-crystalline compounds and/or additives, introducingthe resultant mixture into an LC cell as described above and below, andpolymerising the polymerisable compound(s) with application of anelectrical voltage.

The following meanings apply above and below:

The term “PSA” is, unless indicated otherwise, used to represent PSdisplays and PSA displays.

The terms “tilt” and “tilt angle” relate to a tilted alignment of the LCmolecules of an LC medium relative to the surfaces of the cell in an LCdisplay (here preferably a PS or PSA display). The tilt angle heredenotes the average angle (<90°) between the longitudinal molecular axesof the LC molecules (LC director) and the surface of the plane-parallelouter plates which form the LC cell. A low value of the tilt angle (i.e.a large deviation from the 90° angle) corresponds to a large tilt. Asuitable method for measurement of the tilt angle is given in theexamples. Unless indicated otherwise, tilt angle values disclosed aboveand below relate to this measurement method.

The term “mesogenic group” is known to the person skilled in the art andis described in the literature, and denotes a group which, due to theanisotropy of its attracting and repelling interactions, essentiallycontributes to causing a liquid-crystal (LC) phase inlow-molecular-weight or polymeric substances. Compounds containingmesogenic groups (mesogenic compounds) do not necessarily have to havean LC phase themselves. It is also possible for mesogenic compounds toexhibit LC phase behaviour only after mixing with other compounds and/orafter polymerisation. Typical mesogenic groups are, for example, rigidrod- or disc-shaped units. An overview of the terms and definitions usedin connection with mesogenic or LC compounds is given in Pure Appl.Chem. 73(5), 888 (2001) and C. Tschierske, G. Peizl, S. Diele, Angew.Chem. 2004, 116, 6340-6368.

The term “spacer group”, also referred to as “Sp” above and below, isknown to the person skilled in the art and is described in theliterature, see, for example, Pure Appl. Chem. 73(5), 888 (2001) and C.Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.Unless indicated otherwise, the term “spacer group” or “spacer” aboveand below denotes a flexible group which connects the mesogenic groupand the polymerisable group(s) to one another in a polymerisablemesogenic compound.

The term “reactive mesogen” or “RM” denotes a compound containing amesogenic group and one or more functional groups which are suitable forpolymerisation (also referred to as polymerisable group or group P).

The terms “low-molecular-weight compound” and “unpolymerisable compound”denote compounds, usually monomeric, which contain no functional groupwhich is suitable for polymerisation under the usual conditions known tothe person skilled in the art, in particular under the conditions usedfor the polymerisation of RMs.

For the purposes of this invention, the term “LC medium” is intended todenote a medium which comprises an LC mixture and one or morepolymerisable compounds (such as, for example, reactive mesogens). Theterm “LC mixture” (or “host mixture”) is intended to denote aliquid-crystalline mixture which consists exclusively ofunpolymerisable, low-molecular-weight compounds, preferably of two ormore liquid-crystalline compounds and optionally further additives, suchas, for example, chiral dopants or stabilisers. “Unpolymerisable” meansthat the compounds are stable or unreactive to a polymerisationreaction, at least under the conditions used for polymerisation of thepolymerisable compounds.

Particular preference is given to LC mixtures and LC media which have anematic phase, in particular a nematic phase at room temperature.

The concentration of compounds of the formula I in the LC mixture (i.e.without the polymerisable component) is preferably a 1%, particularlypreferably 1 to 25%, very particularly preferably 2 to 10%.

Particular preference is given to LC mixtures and LC media comprising 1to 5, preferably 1, 2 or 3, compounds of the formula I.

Particular preference is given to compounds of the formula I in which

-   -   L¹ and L² denote H, F or Cl,    -   Z¹, Z² and Z³ are selected from the group consisting of —COO—,        —OCO—, —CF₂O—, —OCF₂, —CH₂O—, —OCH₂— and a single bond, in        particular —COO—, —CH₂O— and a single bond,    -   Z¹ and/or Z³ denote a single bond,    -   m is 0, Z¹ denotes a single bond, and Z² is other than a single        bond,    -   m is 0 and Z² denotes —COO—,    -   m is 0 and Z² denotes —CH₂O—,    -   m is 1 and Z² denotes —COO—,    -   m is 1 and Z² denotes —CH₂O—,    -   m is 1 and Z² denotes a single bond,    -   m is 1 and Z¹, Z² and Z³ denote a single bond,    -   A¹, A², A³ and A⁴ are selected from

-   -   where L¹ and L² have the meaning indicated above and preferably        denote H or F,    -   one or more of the radicals A¹, A², A³ and A⁴, particularly        preferably at least A¹, denotes trans-1,4-cyclohexylene,        1,4-cyclohexenylene, tetrahydropyran-1,4-diyl or        tetrahydropyran-2,5-diyl,    -   R¹ and R² denote straight-chain alkyl or alkoxy having 1 to C        atoms or straight-chain alkenyl having 2 to 7 C atoms.

The compounds of the formula I are preferably selected from the groupconsisting of the following sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote astraight-chain alkyl radical having 1-12, preferably 1-6, C atoms, (O)denotes an oxygen atom or a single bond, (CH═CH) denotes an ethenylenegroup or a single bond, and L denotes H or F.

Particular preference is given to compounds selected from the groupconsisting of the formulae I1, I2, I3, I4, I5, I6, I7, I8 and I9, inparticular those of the formula I1, I2, I3 or I4.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl,s-pentyl, n-hexyl, 2-ethylhexyl, n-heptyl, n-octyl, n-nonyl, n-decyl,n-undecyl, n-dodecyl.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl,pentenyl, hexenyl, heptenyl, octenyl.

Preferred alkoxy groups are, for example, methoxy, ethoxy,2-methoxyethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy,t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy,n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy.

Particularly preferred LC mixtures, LC media and LC displays areindicated below:

-   1) LC mixture or LC medium additionally comprising one or more    compounds of the formulae CY and/or PY:

-   -   in which the individual radicals have the following meanings:    -   a denotes 1 or 2,    -   b denotes 0 or 1,

denotes

-   -   R¹ and R² each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another, preferably alkyl or alkoxy having 1 to        6 C atoms,    -   Z^(x) and Z^(y) each, independently of one another, denote        —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —COO—, —OCO—,        —C₂F₄—, —CF═CF—, —CH═CHCH₂O— or a single bond, preferably a        single bond,    -   L¹⁴ each, independently of one another, denote F, Cl, OCF₃, CF₃,        CH₃, CH₂F, CHF₂.    -   Preferably, both radicals L¹ and L² denote F or one of the        radicals L¹ and L² denotes F and the other denotes Cl, or both        radicals L³ and L⁴ denote F or one of the radicals L³ and L⁴        denotes F and the other denotes Cl.    -   The compounds of the formula CY are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which a denotes 1 or 2, alkyl and alkyl* each, independently        of one another, denote a straight-chain alkyl radical having 1-6        C atoms, and alkenyl denotes a straight-chain alkenyl radical        having 2-6 C atoms, and (O) denotes an oxygen atom or a single        bond. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—,        CH₃—CH═CH—, CH₃—CH₂—CH═CH, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH—        or CH₃—CH═CH—(CH₂)_(r).    -   The compounds of the formula PY are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl denotes a straight-chain alkenyl radical having 2-6 C        atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl        preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   The concentration of an individual compound of the formula CY or        PY in the LC mixture is preferably 2 to 20%.    -   The total concentration of compounds of the formulae CY and PY        in the LC mixture is preferably 1 to 90%, particularly        preferably 10 to 70%.

-   2) LC mixture or LC medium additionally comprising one or more    compounds of the following formula:

-   -   in which the Individual radicals have the following meanings:

denotes

denotes

-   -   R³ and R⁴ each, independently of one another, denote alkyl        having 1 to 12 C atoms, in which, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another,    -   Z^(y) denotes —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,        —COO—, —OCO—, —C₂F₄—, —CF═CF—, —CH═CHCH₂O— or a single bond,        preferably a single bond.    -   The compounds of the formula ZK are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl denotes a straight-chain alkenyl radical having 2-6 C        atoms. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—,        CH₃—CH═CH—, CH₃—CH₂—CH═CH—CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH—        or CH₃—CH═CH—(CH₂)_(r).    -   The concentration of an individual compound of the formula ZK in        the LC mixture is preferably 2 to 20%.

-   3) LC mixture or LC medium additionally comprising one or more    compounds of the following formula:

-   -   in which the individual radicals on each occurrence, Identically        or differently, have the following meanings:    -   R⁵ and R⁶ each, independently of one another, have one of the        meanings indicated above for R¹,

denotes

denotes

-   -   The compounds of the formula DK are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂.    -   Particular preference is given to compounds of the formulae DK1,        DK2, DK4 and DK5.

-   4) LC mixture or LC medium additionally comprising one or more    compounds of the following formula:

-   -   in which the individual radicals have the following meanings;

denotes

-   -   f denotes 0 or 1,    -   R¹ and R² each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or COO— in such a way that O atoms are not linked directly        to one another,    -   Z^(x) and Z^(y) each, independently of one another, denote        —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —COO—, —OCO—,        —C₂F₄—, —CF═CF—, —CH═CHCH₂O— or a single bond, preferably a        single bond,    -   L¹ and L² each, independently of one another, denote F, Cl,        OCF₃, CF₃, CH₃, CH₂F, CHF₂.    -   Preferably, both radicals L¹ and L² denote F or one of the        radicals L¹ and L² denotes F and the other denotes Cl.    -   The compounds of the formula LY are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which R¹ has the meaning indicated above, alkyl denotes a        straight-chain alkyl radical having 1-6 C atoms, (O) denotes an        oxygen atom or a single bond, and v denotes an integer from 1        to 6. R¹ preferably denotes straight-chain alkyl having 1 to 6 C        atoms or straight-chain alkenyl having 2 to 6 C atoms, in        particular CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁, CH₂═CH—,        CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH, CH₃—(CH₂)₂—CH═CH—,        CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.    -   The concentration of an individual compound of the formula LY in        the LC mixture is preferably 2 to 20%.

-   5) LC mixture or LC medium additionally comprising one or more    compounds selected from the group consisting of the following    formulae:

-   -   in which alkyl denotes C₁₋₆-alkyl, L^(x) denotes H or F, and X        denotes F, Cl, OCF₃ OCHF₂ or OCH═CF₂, Particular preference is        given to compounds of the formula G1 in which X denotes F.

-   6) LC mixture or LC medium additionally comprising one or more    compounds selected from the group consisting of the following    formulae:

-   -   in which R⁵ has one of the meanings indicated above for R¹,        alkyl denotes C₁₋₆-alkyl, d denotes 0 or 1, and z and m each,        independently of one another, denote an integer from 1 to 6. R⁵        in these compounds is particularly preferably C₁₋₆-alkyl or        -alkoxy or C₂₋₆-alkenyl, d is preferably 1. The LC medium        according to the invention preferably comprises one or more        compounds of the formulae given above in amounts of ≧5% by        weight.

-   7) LC mixture or LC medium additionally comprising one or more    biphenyl compounds selected from the group consisting of the    following formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   The proportion of the biphenyls of the formulae B1 to B3 in the        LC mixture is preferably at least 3% by weight, in particular        ≧5% by weight.    -   The compounds of the formula B2 are particularly preferred.    -   The compounds of the formulae B1 to B3 are preferably selected        from the group consisting of the following sub-formulae:

-   -   in which alkyl* denotes an alkyl radical having 1-6 C atoms. The        medium according to the invention particularly preferably        comprises one or more compounds of the formulae B1a and/or B2c.

-   8) LC mixture or LC medium additionally comprising one or more    terphenyl compounds of the following formula:

-   -   in which R⁵ and R⁶ each, independently of one another, have one        of the meanings indicated above for R¹, and

each, independently of one another, denote

-   -   in which L⁵ denotes F or Cl, preferably F, and L⁶ denotes F, Cl,        OCF₃, CF₃, CH₃, CH₂F or CHF₂, preferably F.    -   The compounds of the formula T are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which R denotes a straight-chain alkyl or alkoxy radical        having 1-7 C atoms, R* denotes a straight-chain alkenyl radical        having 2-7 C atoms, (O) denotes an oxygen atom or a single bond,        and m denotes an integer from 1 to 6. R* preferably denotes        CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—,        CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.    -   R preferably denotes methyl, ethyl, propyl, butyl, pentyl,        hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.    -   The LC medium according to the invention preferably comprises        the terphenyls of the formula T and the preferred sub-formulae        thereof in an amount of 2-50% by weight, in particular 5-20% by        weight.    -   Particular preference is given to compounds of the formulae T1,        T2, T3 and T21. In these compounds, R preferably denotes alkyl,        furthermore alkoxy, each having 1-5 C atoms.    -   The terphenyls are preferably employed in mixtures according to        the invention if the Δn value of the mixture is to be ≧0.1.        Preferred mixtures comprise 2-20% by weight of one or more        terphenyl compounds of the formula T, preferably selected from        the group of the compounds T1 to T22.

-   9) LC mixture or LC medium additionally comprising one or more    compounds selected from the group consisting of the following    formulae:

-   -   in which R¹ and R² have the meanings indicated above and        preferably each, independently of one another, denote        straight-chain alkyl having 1 to 6 C atoms or straight-chain        alkenyl having 2 to 6 C atoms.    -   Preferred media comprise one or more compounds selected from the        formulae O1, O3 and O4.

-   10) LC mixture or LC medium additionally comprising one or more    compounds of the following formula:

-   -   in which

denotes

-   -   R⁹ denotes H, CH₃, C₂H₅ or n-C₃H₇, (F) denotes an optional        fluorine substituent, and q denotes 1, 2 or 3, and R⁷ has one of        the meanings indicated for R¹, preferably in amounts of >3% by        weight, in particular ≧5% by weight and very particularly        preferably 5-30% by weight.    -   Particularly preferred compounds of the formula FI are selected        from the group consisting of the following sub-formulae:

-   -   in which R⁷ preferably denotes straight-chain alkyl, and R⁹        denotes CH₃, C₂H₅ or n-C₃H₇. Particular preference is given to        the compounds of the formulae FI1, FI12 and FI3.

-   11) LC mixture or LC medium additionally comprising one or more    compounds which contain a tetrahydronaphthyl or naphthyl unit, such    as, for example, the compounds selected from the group consisting of    the following formulae:

-   -   in which R¹⁰ and R¹¹ each, Independently of one another, have        one of the meanings indicated for R¹, preferably denote        straight-chain alkyl or alkoxy having 1 to 6 C atoms or        straight-chain alkenyl having 2 to 6 C atoms, and Z¹ and Z²        each, independently of one another, denote —C₂H₄—, —CH═CH—,        —(CH₂)₄—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CHCH₂CH₂—, —CH₂CH₂CH═CH—,        —CH₂O—, —OCH₂—, —COO—, —OCO—, —C₂F₄—, —CF═CF—, —CF═CH—, —CH═CF—,        —CH₂— or a single bond.

-   12) LC mixture or LC medium additionally comprising one or more    difluorodibenzochromans and/or chromans of the following formulae:

-   -   in which R¹¹ and R¹² each, independently of one another, have        the meanings indicated above, and c denotes 0 or 1, preferably        in amounts of 3 to 20% by weight, in particular in amounts of 3        to 15% by weight.    -   Particularly preferred compounds of the formulae BC and CR are        selected from the group consisting of the following        sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   Very particular preference is given to mixtures comprising one,        two or three compounds of the formula BC-2.

-   13) LC mixture or LC medium additionally comprising one or more    fluorinated phenanthrenes and/or dibenzofurans of the following    formulae:

-   -   in which R¹¹ and R¹² each, independently of one another, have        the meanings indicated above, b denotes 0 or 1, L denotes F, and        r denotes 1, 2 or 3.    -   Particularly preferred compounds of the formulae PH and BF are        selected from the group consisting of the following        sub-formulae:

-   -   in which R and R′ each, independently of one another, denote a        straight-chain alkyl or alkoxy radical having 1-7 C atoms.

-   14) LC mixture which comprises no compounds, in particular no    mesogenic or liquid-crystalline compounds, that contain one or more    alkenyl groups or that contain one or more alkyl groups in which one    or more CH₂ groups have been replaced by CH═CH and optionally    additionally by other groups.

-   15) LC mixture comprising one or more compounds selected from the    group consisting of formula CY in which a=1, formula PY in which b=0    and formula LY in which f=0, in a total concentration of 1 to 60%.

-   16) LC mixture comprising one or more compounds selected from the    group consisting of formula CY in which a=2 and formula PY in which    b=1, in a total concentration of 1 to 60%.

-   17) LC mixture comprising one or more compounds selected from the    group consisting of formula CY in which a=2 and R¹, R² denote an    alkyl or alkenyl group, and formula T, in a total concentration of 1    to 50%.

-   18) LC mixture comprising one or more compounds selected from the    group consisting of formulae ZK1, ZK2, ZK5, ZK6, DK1, DK2, DK4, DK5,    B1 and T1, in a total concentration of 1 to 60%.

-   19) LC mixture comprising one or more compounds of the formulae ZK1    and/or ZK2 in a total concentration of 1 to 40%.

-   20) LC mixture comprising one or more compounds selected from the    group consisting of formulae ZK3, ZK4, B2 and B3, in a total    concentration of 1 to 70%.

-   21) LC mixture comprising one or more compounds of the formula FI in    a total concentration of 1 to 25%.

-   22) LC medium in which the concentration of the polymerisable    component or component A) is ≦5%, preferably ≦1%, particularly    preferably ≦0.5%, and preferably ≧0.01%, particularly preferably    a≧0.1%.

-   23) LC medium in which the concentration of the liquid-crystalline    component (LC mixture) or component B) is ≧95%, particularly    preferably ≧99%.

-   24) LC medium which, apart from the polymerisable compounds of    component A, comprises no compounds that contain a terminal vinyloxy    group (—O—CH═CH₂).

-   25) PSA-VA display in which the pretilt angle is preferably ≦85°,    particularly preferably 80°.

The individual components of the preferred embodiments 1)-21) of the LCmixtures according to the invention are either known or theirpreparation processes can readily be derived from the prior art by theperson skilled in the relevant art, since they are based on standardmethods described in the literature. Corresponding compounds of theformula CY are described, for example, in EP-A-0 364 538. Correspondingcompounds of the formula ZK are described, for example, in DE-A-26 36684 and DE-A-33 21 373.

The combination of LC mixtures of the preferred embodiments 1)-21)indicated above with the polymerised compounds indicated above and belowcauses low threshold voltages, low rotational viscosities and very goodlow-temperature stabilities in the LC media according to the inventionat the same time as constantly high clearing points and high HR valuesand allows a particularly low pretilt angle to be established quickly inPSA displays. In particular, the LC media in PSA displays exhibitsignificantly shortened response times, in particular also thegrey-shade response times, compared with the media from the prior art.

The LC mixture preferably has a nematic phase range of at least 80 K,particularly preferably at least 100 K, and a rotational viscosity ofnot more than 250 mPa·s, preferably not more than 200 mPa·s, at 20° C.

In the VA-type displays according to the invention, the molecules in thelayer of the LC medium in the switched-off state are alignedperpendicular to the electrode surfaces (homeotropically) or have atilted homeotropic alignment. On application of an electrical voltage tothe electrodes, a realignment of the LC molecules with the longitudinalmolecular axes parallel to the electrode surfaces takes place.

LC mixtures according to the invention for use in displays of the VAtype have a negative dielectric anisotropy Δ∈, preferably of −0.5 to−10, in particular −2.5 to −7.5, at 20° C. and 1 kHz.

The birefringence Δn in LC mixtures according to the invention for usein displays of the VA type is preferably below 0.16, particularlypreferably between 0.06 and 0.14, in particular between 0.07 and 0.12.

The LC mixtures and LC media according to the invention may alsocomprise further additives known to the person skilled in the art anddescribed in the literature, such as, for example, polymerisationInitiators, inhibitors, stabilisers, surface-active substances or chiraldopants. These may be polymerisable or unpolymerisable. Polymerisableadditives are accordingly classed in the polymerisable component orcomponent A). Unpolymerisable additives are accordingly classed in theLC mixture (host mixture) or the unpolymerisable component or componentB).

The LC mixtures and LC media may comprise, for example, one or morechiral dopants, preferably selected from the group consisting ofcompounds from Table B below.

However, LC media with no chiral or optically active components aregenerally preferred.

Furthermore, 0 to 15%, preferably 0 to 10%, of one or more additivesselected from the group comprising pleochroic dyes, nanoparticles,conductive salts, complex salts and substances for modifying thedielectric anisotropy, the viscosity and/or the alignment of the nematicphases can be added to the LC media. Suitable and preferred conductivesalts are, for example, ethyldimethyldodecylammonium 4-hexoxybenzoate,tetrabutylammonium tetraphenylborate or complex salts of crown ethers(cf., for example, Hailer et al., Mol. Cryst. Liq. Cryst. 24, 249-258,1973). Substances of this type are described, for example, in DE-A-22 09127, DE-A-22 40 864, DE-A-23 21 632, DE-A-23 38 281, DE-A-24 50 088,DE-A-26 37 430 and DE-A-28 53 728.

For the production of PSA displays, the polymerisable compounds arepolymerised or crosslinked (if a compound contains two or morepolymerisable groups) by in-situ polymerisation in the LC medium betweenthe substrates of the LC display with application of a voltage. Thepolymerisation can be carried out in one step. It is also possiblefirstly to carry out the polymerisation in a first step with applicationof a voltage in order to generate a pretilt angle, and subsequently, ina second polymerisation step, to polymerise or crosslink the compoundswhich have not reacted in the first step without an applied voltage (endcuring).

Suitable and preferred polymerisation methods are, for example, thermalor photopolymerisation, preferably photopolymerisation, in particular UVphotopolymerisation. If necessary, one or more initiators may also beadded here. Suitable conditions for the polymerisation, and suitabletypes and amounts of initiators, are known to the person skilled in theart and are described in the literature. For example, the commerciallyavailable photoinitiators Irgacure651, Irgacure184®, Irgacure907®,Irgacure369® or Darocure1173® (Ciba AG) are suitable for free-radicalpolymerisation. If an initiator is employed, its proportion ispreferably 0.001 to 5%, particularly preferably 0.001 to 1%. However,the polymerisation can also be carried out without addition of aninitiator. In a further preferred embodiment, the LC medium does notcomprise a polymerisation initiator.

The polymerisable component A) or the LC medium may also comprise one ormore stabilisers in order to prevent undesired spontaneouspolymerisation of the RMs, for example during storage or transport.Suitable types and amounts of stabilisers are known to the personskilled in the art and are described in the literature. For example, thecommercially available stabilisers from the Irganox® series (Ciba AG),such as, for example, Irganox® 1076, are particularly suitable. Ifstabilisers are employed, their proportion, based on the total amount ofthe RMs or the polymerisable component A), is preferably 10-10,000 ppm,particularly preferably 50-500 ppm.

The polymerisable compounds are also suitable for polymerisation withoutinitiator, which is accompanied by considerable advantages, such as, forexample, lower material costs and in particular less contamination ofthe LC medium by possible residual amounts of the initiator ordegradation products thereof.

The LC media according to the invention for use in PSA displayspreferably comprise ≦5%, particularly preferably ≦1%, very particularlypreferably ≦0.5%, and preferably ≧0.01%, particularly preferably ≧0.1%,of polymerisable compounds, in particular polymerisable compounds of theformulae given above and below.

Particular preference is given to LC media comprising one, two or threepolymerisable compounds.

Preference is furthermore given to achiral polymerisable compounds andto LC media in which the compounds of component A) and/or B) areselected exclusively from the group consisting of achiral compounds.

Preference is furthermore given to LC media in which the polymerisablecomponent or component A) comprises one or more polymerisable compoundscontaining one polymerisable group (monoreactive) and one or morepolymerisable compounds containing two or more, preferably two,polymerisable groups (di- or multireactive).

Preference is furthermore given to PSA displays and LC media in whichthe polymerisable component or component A) comprises exclusivelypolymerisable compounds containing two polymerisable groups(direactive).

The polymerisable compounds can be added individually to the LC media,but it is also possible to use mixtures comprising two or morepolymerisable compounds according to the invention. In the case ofpolymerisation of such mixtures, copolymers are formed. The inventionfurthermore relates to the polymerisable mixtures mentioned above andbelow. The polymerisable compounds can be mesogenic or non-mesogenic.Particular preference is given to polymerisable mesogenic compounds,also known as reactive mesogens (RMs).

Suitable and preferred RMs for use in LC media and PSA displaysaccording to the invention are described below.

In a preferred embodiment of the invention, the polymerisable compoundsare selected from formula I*

R^(a)—B¹—(Z^(b)—B²)_(m)—R^(b)  I*

in which the individual radicals have the following meanings:

-   R^(a) and R^(b) each, independently of one another, denote P, P-Sp-,    H, halogen, SF₅, NO₂, a carbon group or hydrocarbon group, where at    least one of the radicals R^(a) and R^(b) denotes or contains a    group P or P-Sp-, and where, if B¹ and/or B² contain a saturated C    atom, R^(a) and/or R^(b) may also denote a radical which is    spiro-linked to this saturated C atom,-   P on each occurrence, identically or differently, denotes a    polymerisable group,-   Sp on each occurrence, identically or differently, denotes a spacer    group or a single bond,-   B¹ and B² each, independently of one another, denote an aromatic,    heteroaromatic, alicyclic or heterocyclic group, preferably having 4    to 25 ring atoms, which may also contain fused rings, and which may    also be mono- or polysubstituted by L,-   L denotes P-Sp-, H, OH, CH₂OH, halogen, SF₅, NO₂, a carbon group or    hydrocarbon group,-   Z^(b) on each occurrence, identically or differently, denotes —O—,    —S—, —CO—, —CO—O—, —OCO—, —O—CO—O—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—,    —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —(CH₂)_(n1)—, —CF₂CH₂—, —CH₂CF₂—,    —(CF₂)_(n1)—, —CH═CH—, —CF═CF—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—,    CR⁰R⁰⁰ or a single bond,-   R⁰ and R⁰⁰ each, independently of one another, denote H or alkyl    having 1 to 12 C atoms,-   m denotes 0, 1, 2, 3 or 4,-   n1 denotes 1, 2, 3 or 4.

Particularly preferred compounds of the formula I* are those in which

-   R^(a) and R^(b) each, independently of one another, denote P, P-Sp-,    H, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN, SF₅ or    straight-chain or branched alkyl having 1 to 25 C atoms, in which,    in addition, one or more non-adjacent CH₂ groups may each be    replaced, independently of one another, by —C(R⁰)═C(R⁰⁰)—, —C≡C—,    —N(R⁰⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way    that O and/or S atoms are not linked directly to one another, and in    which, in addition, one or more H atoms may be replaced by F, Cl,    Br, I, CN, P or P-Sp-, where at least one of the radicals R^(a) and    R^(b) denotes or contains a group P or P-Sp-, where, if B¹ and/or B²    contain a saturated C atom, R^(a) and/or R^(b) may also denote a    radical which is spiro-linked to this saturated C atom,-   B¹ and B² each, independently of one another, denote 1,4-phenylene,    naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-2,7-diyl,    anthracene-2,7-diyl, fluorene-2,7-diyl, coumarine, flavone, where,    in addition, one or more CH groups in these groups may be replaced    by N, cyclohexane-1,4-diyl, in which, in addition, one or more    non-adjacent CH₂ groups may be replaced by O and/or S,    1,4-cyclohexenylene, bicycle[1.1.1]-pentane-1,3-diyl,    bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]-heptane-2,6-diyl,    piperidine-1,4-diyl, decahydronaphthalene-2,6-diyl,    1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl or    octahydro-4,7-methanoindane-2,5-diyl, where all these groups may be    unsubstituted or mono- or polysubstituted by L,-   L denotes P, P-Sp-, OH, CH₂OH, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS,    —OCN, —SCN, —C(═O)N(R^(x))₂, —C(═O)Y¹, —C(═O)R^(x), —N(R^(x))₂,    optionally substituted silyl, optionally substituted aryl having 6    to 20 C atoms, or straight-chain or branched alkyl, alkoxy,    alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy    having 1 to 25 C atoms, in which, in addition, one or more H atoms    may be replaced by F, Cl, P or P-Sp-,-   P and Sp have the meanings indicated above,-   Y¹ denotes halogen,-   R^(x) denotes P, P-Sp-, H, halogen, straight-chain, branched or    cyclic alkyl having 1 to 25 C atoms, in which, in addition, one or    more non-adjacent CH₂ groups may be replaced by —O—, —S—, —CO—,    —CO—O—, —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not    linked directly to one another, and in which, in addition, one or    more H atoms may be replaced by F, Cl, P or P-Sp-, an optionally    substituted aryl or aryloxy group having 6 to 40 C atoms, or an    optionally substituted heteroaryl or heteroaryloxy group having 2 to    40 C atoms.

Particularly preferred compounds of the formula I* are selected from thefollowing sub-formulae:

in which the individual radicals have the following meanings:

-   P¹ and P² each, independently of one another, denote a polymerisable    group, preferably having one of the meanings indicated above and    below for P, particularly preferably an acrylate, methacrylate,    fluoroacrylate, oxetane, vinyloxy or epoxy group,-   Sp¹ and Sp² each, independently of one another, denote a single bond    or a spacer group, preferably having one of the meanings indicated    above and below for Sp, and particularly preferably —(CH₂)_(p1)—,    —(CH₂)_(p1)—O—, —(CH₂)_(p1)—CO—O— or —(CH₂)_(p1)—O—CO—O—, in which    p1 is an integer from 1 to 12, and where the linking to the adjacent    ring in the last-mentioned groups takes place via the O atom,-   and where one or more of the radicals P¹-Sp¹- and P²-Sp²- may denote    R^(aa), with the proviso that at least one of the radicals P¹-Sp¹-    and P²-Sp²- present does not denote R^(aa),-   R^(aa) denotes H, F, Cl, CN or straight-chain or branched alkyl    having 1 to 25 C atoms, in which, in addition, one or more    non-adjacent CH₂ groups may each be replaced, independently of one    another, by C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰)—, —O—, —S—, —CO—, —CO—O—,    —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linked    directly to one another, and in which, in addition, one or more H    atoms may be replaced by F, Cl, CN or P¹-Sp¹-, particularly    preferably straight-chain or branched, optionally mono- or    polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,    alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12    C atoms (where the alkenyl and alkynyl radicals have at least two C    atoms and the branched radicals have at least three C atoms),-   R⁰, R⁰⁰ each, independently of one another and Identically or    differently on each occurrence, denote H or alkyl having 1 to 12 C    atoms,-   R^(y) and R^(z) each, independently of one another, denote H, F, CH₃    or CF₃,-   Z¹ denotes —O—, —CO—, —C(R^(y)R^(z))—, or —CF₂CF₂—,-   Z² and Z³ each, independently of one another, denote —CO—O—, —O—CO—,    —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or —(CH₂)_(n)—, where n is 2, 3 or 4,-   L on each occurrence, identically or differently, denotes F, Cl, CN    or straight-chain or branched, optionally mono- or polyfluorinated    alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl,    alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms,    preferably F,-   L′ and L″ each, independently of one another, denote H, F or Cl,-   r denotes 0, 1, 2, 3 or 4,-   r denotes 0, 1, 2 or 3,-   t denotes 0, 1 or 2,-   x denotes 0 or 1.

In a preferred embodiment, the LC media comprise one or more, preferablyexclusively, RMs selected from the group consisting of compounds of theformula I*, or sub-formulae thereof, which contain precisely one radicalP-Sp- or P¹-Sp¹ or P²-Sp² in which Sp or Sp¹ or Sp² denotes a singlebond and precisely one radical P-Sp- or P¹-Sp¹ or P²-Sp² in which Sp orSp¹ or Sp² is not a single bond (“monospacer compounds”).

In a further preferred embodiment of the invention, the polymerisablecompounds are chiral or optically active compounds selected from formulaII*(chiral RMs):

(R*—(B¹—Z^(b))_(m))_(k)-Q  II*

in which B¹, Z^(b) and m have on each occurrence, identically ordifferently, one of the meanings indicated in formula I*,

-   R* has on each occurrence, identically or differently, one of the    meanings indicated for R_(a) in formula I*, where R* can be chiral    or achiral,-   Q denotes a k-valent chiral group, which is optionally mono- or    polysubstituted by L, as defined in formula I*,-   k is 1, 2, 3, 4, 5 or 6,    where the compounds contain at least one radical R* or L which    denotes or contains a group P or P-Sp- as defined above.

Particularly preferred compounds of the formula II* contain a monovalentgroup Q of the formula III*

in which L and r have on each occurrence, identically or differently,the meanings indicated above,

-   A* and B* each, independently of one another, denote fused benzene,    cyclohexane or cyclohexene,-   t on each occurrence, Identically or differently, denotes 0, 1 or 2,    and-   u on each occurrence, identically or differently, denotes 0, 1 or 2.

Particular preference is given to groups of the formula III* in which udenotes 1.

Further preferred compounds of the formula II* contain a monovalentgroup Q or one or more groups R* of the formula IV*

in which

-   Q¹ denotes alkylene or alkyleneoxy having 1 to 9 C atoms or a single    bond,-   Q² denotes optionally fluorinated alkyl or alkoxy having 1 to 10 C    atoms, in which, in addition, one or two non-adjacent CH₂ groups may    be replaced by —O—, —S—, —CH═CH—, —CO—, —OCO—, —COO—, —O—COO—,    —S—CO—, —CO—S— or —C≡C— in such a way that O and/or S atoms are not    linked directly to one another,-   Q³ denotes F, Cl, CN or alkyl or alkoxy as defined for Q², but    different from Q².

Preferred groups of the formula IV* are, for example, 2-butyl(=1-methylpropyl), 2-methylbutyl, 2-methylpentyl, 3-methylpentyl,2-ethylhexyl, 2-propylpentyl, in particular 2-methylbutyl,2-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy,1-methylhexoxy, 2-octyloxy, 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl,4-methylhexyl, 2-hexyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl,6-methoxyoctoxy, 6-methyloctoxy, 6-methyloctanoyloxy,5-methylheptyloxycarbonyl, 2-methylbutyryloxy, 3-methylvaleroyloxy,4-methylhexanoyloxy, 2-chloropropionyloxy, 2-chloro-3-methylbutyryloxy,2-chloro-4-methylvaleryloxy, 2-chloro-3-methylvaleryloxy,2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl, 1-methoxypropyl-2-oxy,1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy, 1-butoxypropyl-2-oxy,2-fluorooctyloxy, 2-fluorodecyloxy, 1,1,1-trifluoro-2-octyloxy,1,1,1-trifluoro-2-octyl, 2-fluoromethyloctyloxy.

Further preferred compounds of the formula II* contain a divalent groupQ of the formula V*

in which L, r, t, A* and B* have the meanings indicated above.

Further preferred compounds of the formula II* contain a divalent groupQ selected from the following formulae:

in which Phe denotes phenyl, which is optionally mono- orpolysubstituted by L, and Rx denotes F or optionally fluorinated alkylhaving 1 to 4 C atoms.

Suitable chiral RMs are described, for example, in GB 2 314 839 A, U.S.Pat. No. 6,511,719, U.S. Pat. No. 7,223,450, WO 02/34739 A1, U.S. Pat.No. 7,041,345, U.S. Pat. No. 7,060,331 or U.S. Pat. No. 7,318,950.Suitable RMs containing binaphthyl groups are described, for example, inU.S. Pat. No. 6,818,261, U.S. Pat. No. 6,916,940, U.S. Pat. No.7,318,950 and U.S. Pat. No. 7,223,450.

The chiral structural elements shown above and below and polymerisableand polymerised compounds containing such chiral structural elements canbe employed in optically active form, i.e. as pure enantiomers or as anydesired mixture of the two enantiomers, or alternatively as a racemate.The use of racemates is preferred. The use of racemates has someadvantages over the use of pure enantiomers, such as, for example,significantly lower synthesis complexity and lower material costs. Inaddition, the use of racemates enables an undesired twist of the LCmolecules in the LC display to be avoided.

Particularly preferred compounds of the formula II* are selected fromthe following sub-formulae:

in which L, P, Sp, m, r and t have the meanings indicated above, Z and Ahave on each occurrence, identically or differently, one of the meaningsindicated for Z¹ and A¹ respectively, and t1 on each occurrence,identically or differently, denotes 0 or 1.

The term “carbon group” denotes a mono- or polyvalent organic groupcontaining at least one carbon atom, where this either contains nofurther atoms (such as, for example, —C≡C—) or optionally contains oneor more further atoms, such as, for example, N, O, S, P, Si, Se, As, Teor Ge (for example carbonyl, etc.). The term “hydrocarbon group” denotesa carbon group which additionally contains one or more H atoms andoptionally one or more heteroatoms, such as, for example, N, O, S, P,Si, Se, As, Te or Ge.

“Halogen” denotes F, Cl, Br or I.

A carbon or hydrocarbon group can be a saturated or unsaturated group.Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. Acarbon or hydrocarbon radical having more than 3 C atoms can bestraight-chain, branched and/or cyclic and may also contain spiro linksor condensed rings.

The terms “alkyl”, “aryl”, “heteroaryl”, etc., also encompass polyvalentgroups, for example alkylene, arylene, heteroarylene, etc.

The term “aryl” denotes an aromatic carbon group or a group derivedtherefrom. The term “heteroaryl” denotes “aryl” as defined above,containing one or more heteroatoms.

Preferred carbon and hydrocarbon groups are optionally substitutedalkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl,alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to25, particularly preferably 1 to 18, C atoms, optionally substitutedaryl or aryloxy having 6 to 40, preferably 6 to 25, C atoms, oroptionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkyloxy,arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxyhaving 6 to 40, preferably 6 to 25, C atoms.

Further preferred carbon and hydrocarbon groups are C₁-C₄₀ alkyl, C₂-C₄₀alkenyl, C₂-C₄₀ alkynyl, C₃-C₄₀ allyl, C₄-C₄₀ alkyldienyl, C₄-C₄₀polyenyl, C₆-C₄₀ aryl, C₆-C₄₀ alkylaryl, C₆-C₄₀ arylalkyl, C₆-C₄₀alkylaryloxy, C₆-C₄₀ arylalkyloxy, C₂-C₄₀ heteroaryl, C₄-C₄₀ cycloalkyl,C₄-C₄₀ cycloalkenyl, etc. Particular preference is given to C₁-C₂₂alkyl, C₂-C₂₂ alkenyl, C₂-C₂₂ alkynyl, C₃-C₂₂ allyl, C₄-C₂₂ alkyldienyl,C₆-C₁₂ aryl, C₆-C₂₀ arylalkyl and C₂-C₂₀ heteroaryl.

Further preferred carbon and hydrocarbon groups are straight-chain,branched or cyclic alkyl radicals having 1 to 40, preferably 1 to 25, Catoms, which are unsubstituted or mono- or polysubstituted by F, Cl, Br,I or CN and in which one or more non-adjacent CH₂ groups may each bereplaced, independently of one another, by —C(R^(x))═C(R^(x))—, —C≡C—,—N(R^(x))—, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way thatO and/or S atoms are not linked directly to one another.

R^(x) preferably denotes H, halogen, a straight-chain, branched orcyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one ormore non-adjacent C atoms may be replaced by —O—, —S—, —CO—, —CO—O—,—O—CO—, —O—CO—O— and in which one or more H atoms may be replaced byfluorine, an optionally substituted aryl or aryloxy group having 6 to 40C atoms, or an optionally substituted heteroaryl or heteroaryloxy grouphaving 2 to 40 C atoms.

Preferred alkoxy groups are, for example, methoxy, ethoxy,2-methoxyethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy,t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy,n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy, etc.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl,s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl,cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl,n-dodecyl, dodecanyl, trifluoromethyl, perfluoro-n-butyl,2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, etc.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl,pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl,octenyl, cyclooctenyl, etc.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl,pentynyl, hexynyl, octynyl, etc.

Preferred alkoxy groups are, for example, methoxy, ethoxy,2-methoxyethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy,t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy,n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy, etc.

Preferred amino groups are, for example, dimethylamino, methylamino,methylphenylamino, phenylamino, etc.

Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e. theycan contain one ring (such as, for example, phenyl) or two or morerings, which may also be fused (such as, for example, naphthyl) orcovalently bonded (such as, for example, biphenyl), or contain acombination of fused and linked rings. Heteroaryl groups contain one ormore heteroatoms, preferably selected from O, N, S and Se.

Particular preference is given to mono-, bi- or tricyclic aryl groupshaving 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl groupshaving 2 to 25 C atoms, which optionally contain fused rings and areoptionally substituted.

Preference is furthermore given to 5-, 6- or 7-membered aryl andheteroaryl groups, in which, in addition, one or more CH groups may bereplaced by N, S or O in such a way that O atoms and/or S atoms are notlinked directly to one another.

Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl,[1,1′:3′,1″]terphenyl-2′-yl, naphthyl, anthracene, binaphthyl,phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene,pentacene, benzopyrene, fluorene, indene, indenofluorene,spirobifluorene, etc.

Preferred heteroaryl groups are, for example, 5-membered rings, such aspyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole,furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole,1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole,1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole,1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings, such aspyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine,1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine,1,2,3,5-tetrazine, or condensed groups, such as indole, isoindole,indolizine, indazole, benzlmidazole, benzotriazole, purine,naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole,quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole,phenanthroxazole, isoxazole, benzothlazole, benzofuran, isobenzofuran,dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline,benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine,phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine,quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline,phenanthridine, phenanthroline, thieno[2,3b]-thiophene,thieno[3,2b]thiophene, dithlenothiophene, isobenzothiophene,dibenzothiophene, benzothiadiazothiophene, or combinations of thesegroups. The heteroaryl groups may also be substituted by alkyl, alkoxy,thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.

The (non-aromatic) alicyclic and heterocyclic groups encompass bothsaturated rings, i.e. those containing exclusively single bonds, andalso partially unsaturated rings, i.e. those which may also containmultiple bonds. Heterocyclic rings contain one or more heteroatoms,preferably selected from Si, O, N, S and Se.

The (non-aromatic) alicyclic and heterocyclic groups can be monocyclic,i.e. contain only one ring (such as, for example, cyclohexane), orpolycyclic, i.e. contain a plurality of rings (such as, for example,decahydronaphthalene or bicyclooctane). Particular preference is givento saturated groups. Preference is furthermore given to mono-, bi- ortricyclic groups having 3 to 25 C atoms, which optionally contain fusedrings and are optionally substituted. Preference is furthermore given to5-, 6-, 7- or 8-membered carbocyclic groups, in which, in addition, oneor more C atoms may be replaced by Si and/or one or more CH groups maybe replaced by N and/or one or more non-adjacent CH₂ groups may bereplaced by —O— and/or —S—.

Preferred alicyclic and heterocyclic groups are, for example, 5-memberedgroups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran,pyrrolidine, 6-membered groups, such as cyclohexane, silinane,cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane,1,3-dithiane, piperidine, 7-membered groups, such as cycloheptane, andfused groups, such as tetrahydronaphthalene, decahydronaphthalene,indane, bicyclo[1.1.1]-pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.

Preferred substituents are, for example, solubility-promoting groups,such as alkyl or alkoxy, electron-withdrawing groups, such as fluorine,nitro or nitrile, or substituents for increasing the glass transitiontemperature (Tg) in the polymer, in particular bulky groups, such as,for example, t-butyl or optionally substituted aryl groups.

Preferred substituents, also referred to as “L” above and below, are,for example, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN,—C(═O)N(R^(x))₂, —C(═O)Y¹, —C(═O)R^(x), —N(R^(x))₂, in which R^(x) hasthe meaning indicated above, and Y¹ denotes halogen, optionallysubstituted silyl or aryl having 6 to 40, preferably 6 to 20, C atoms,and straight-chain or branched alkyl, alkoxy, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 Catoms, in which one or more H atoms may optionally be replaced by F orCl.

“Substituted silyl or aryl” preferably means substituted by halogen,—CN, R⁰, —OR⁰, —CO—R⁰, —CO—O—R⁰, —O—CO—R⁰ or —O—CO—O—R⁰, in which R⁰ hasthe meaning indicated above.

Particularly preferred substituents L are, for example, F, Cl, CN, NO₂,CH₃, C₂H₅, OCH₃, OC₂Hs, COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF₃,OCHF₂, OC₂F₅, furthermore phenyl.

is preferably

in which L has one of the meanings indicated above.

The polymerisable group P is a group which is suitable for apolymerisation reaction, such as, for example, free-radical or ionicchain polymerisation, polyaddition or polycondensation, or for apolymer-analogous reaction, for example addition or condensation onto amain polymer chain. Particular preference is given to groups for chainpolymerisation, in particular those containing a C═C double bond or—C≡C— triple bond, and groups which are suitable for polymerisation withring opening, such as, for example, oxetane or epoxy groups.

Preferred groups P are selected from CH₂═CW¹—COO—, CH₂═CW¹—CO—,

CH₂═CW²—(O)_(k3)—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—, CH₂═CW¹—CO—NH—,CH₃—CH═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—,(CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, HO—CW²W³—, HS—CW²W³—, HW²N—,HO—CW²W³—NH—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—,CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH—, HOOC—, OCN— and W⁴W⁵W⁶Si—,in which WI denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 Catoms, in particular H, F, C₁ or CH₃, W² and W³ each, independently ofone another, denote H or alkyl having 1 to 5 C atoms, in particular H,methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of oneanother, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms,W⁷ and W⁸ each, independently of one another, denote H, Cl or alkylhaving 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionallysubstituted by one or more radicals L as defined above which aredifferent from P-Sp-, k₁, k₂ and k₃ each, independently of one another,denote 0 or 1, k₃ preferably denotes 1.

Particularly preferred groups P are CH₂═CW¹—COO—, in particularCH₂═CH—COO—, CH₂═C(CH₃)—COO— and CH₂═CF—COO—, furthermore CH₂═CH—O—,(CH₂═CH)₂CH—OCO—, (H₂═CH)₂CH—O—,

Very particularly preferred groups P are vinyloxy, acrylate,methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, inparticular acrylate and methacrylate.

Preferred spacer groups Sp are selected from the formula Sp′-X′, so thatthe radical P-Sp- corresponds to the formula P-Sp′-X′—, where

-   Sp′ denotes alkylene having 1 to 20, preferably 1 to 12, C atoms,    which is optionally mono- or polysubstituted by F, Cl, Br, I or CN    and in which, in addition, one or more non-adjacent CH₂ groups may    each be replaced, independently of one another, by —O—, —S—, —NH—,    —NR⁰—, —SiR⁰⁰R⁰⁰⁰—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—,    —NR⁰⁰—CO—O—, —O—CO—NR⁰⁰—, —NR⁰⁰—CO—NR⁰⁰—, —CH═CH— or —C≡C— in such a    way that O and/or S atoms are not linked directly to one another,-   X′ denotes —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰⁰—,    —NR⁰⁰—CO—, —NR⁰⁰—CO—NR⁰⁰—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—,    —OCF₂—, —CF₂S—, —SCF₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═N—,    —N═CH—, —N═N—, —CH═CR⁰—, —CY²═CY³—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—    or a single bond,-   R⁰⁰ and R⁰⁰⁰ each, independently of one another, denote H or alkyl    having 1 to 12 C atoms, and-   Y² and Y³ each, independently of one another, denote H, F, Cl or CN.

X′ is preferably —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰—,—NR⁰—CO—, —NR⁰—CO—NR⁰— or a single bond.

Typical spacer groups Sp′ are, for example, —(CH₂)_(p1)—,—(CH₂CH₂O)_(q1)—CH₂CH₂, —CH₂CH₂—S—CH₂CH₂—, —CH₂CH₂—NH—CH₂CH₂— or—(SiR⁰⁰R⁰⁰⁰—O)_(p1)—, In which p1 is an integer from 1 to 12, q1 is aninteger from 1 to 3, and R⁰⁰ and R⁰⁰⁰ have the meanings indicated above.

Particularly preferred groups —X′-Sp′- are —(CH₂)_(p1)—, —O—(CH₂)_(p1)—,—OCO—(CH₂)_(p1)—, —OCOO—(CH₂)_(p1)—.

Particularly preferred groups Sp′ are, for example, in each casestraight-chain ethylene, propylene, butylene, pentylene, hexylene,heptylene, octylene, nonylene, decylene, undecylene, dodecylene,octadecylene, ethyleneoxyethylene, methyleneoxybutylene,ethylenethioethylene, ethylene-N-methyliminoethylene, 1-methylalkylene,ethenylene, propenylene and butenylene.

In a further preferred embodiment of the invention, P-Sp- denotes aradical containing two or more polymerisable groups (multifunctionalpolymerisable radicals). Suitable radicals of this type andpolymerisable compounds containing them and the preparation thereof aredescribed, for example, in U.S. Pat. No. 7,060,200 B1 or US 200610172090A1. Particular preference is given to multifunctional polymerisableradicals P-Sp- selected from the following formulae:

—X-alkyl-CHP¹—CH₂—CH₂P²  I*a

—X-alkyl-C(CH₂P¹)(CH₂P²)—CH₂P³  I*b

—X-alkyl-CH₂P¹CHP²—CH₂P³  I*c

—X-alkyl-C(CH₂P¹)(CH₂P²)—C_(aa)H_(2aa+1)  I*d

—X-alkyl-CHP¹—CH₂P²  I*e

—X-alkyl-CHP¹P²  I*f

—X-alkyl-CP¹P²—C_(aa)H_(2aa+1)  I*g

—X-alkyl-C(CH₂P¹)(CH₂P2)—CH₂OCH₂—C(CH₂P³)(CH₂P⁴)CH₂P⁵  I*h

—X-alkyl-CH((CH₂)_(aa)P¹)((CH₂)_(bb)P²)  I*i

—X-alkyl-CH P¹CHP²—C_(aa)H_(2aa+1)  I*k

—X′-alkyl-C(CH₃)(CH₂P¹)(CH₂P²)  I*m

in which

-   alkyl denotes a single bond or straight-chain or branched alkylene    having 1 to 12 C atoms, in which one or more non-adjacent CH₂ groups    may each be replaced, independently of one another, by    —C(R⁰⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—,    —O—CO—O— in such a way that O and/or S atoms are not linked directly    to one another and in which, in addition, one or more H atoms may be    replaced by F, Cl or CN, where R⁰⁰ and R⁰⁰⁰ have the meanings    indicated above,-   aa and bb each, independently of one another, denote 0, 1, 2, 3, 4,    5 or 6,-   X has one of the meanings indicated for X′, and-   P¹⁻⁵ each, independently of one another, have one of the meanings    indicated for P.

Preference is furthermore given to compounds of the formula I* andsub-formulae thereof in which B¹ and/or B² denote an at least partiallysaturated radical, preferably cyclohexylene, in which R^(a) and/or R^(b)denote P- or P-Sp and are linked to an sp³-hybridised C atom of thisradical B¹ or B² and in which this sp³-hybridised C atom contains, asfurther substituent, a radical P (or P^(1/2)) or P-Sp- (or P¹-Sp¹- orP²-Sp²-), which preferably has the same meaning as the radical R^(a) orR^(b) linked to the same sp³ C atom. Particularly preferred compoundscontain a structural element of the formula

—C^(sp)((CH₂)_(aa)P¹)((CH₂)_(bb)P²)  I*n

in which C^(sp3) denotes the sp³-hybridized C atom in the radical B¹ orB², and P¹, P², aa and bb have the meanings indicated above.

The polymerisable compounds and RMs can be prepared analogously toprocesses known to the person skilled in the art and described instandard works of organic chemistry, such as, for example, inHouben-Weyl, Methoden der organischen Chemie [Methods of OrganicChemistry], Thieme-Verlag, Stuttgart. Further synthetic methods aregiven in the documents cited above and below. In the simplest case, thesynthesis of such RMs is carried out, for example, by esterification oretherification of 2,6-dihydroxynaphthalene or 4,4′-dihydroxybiphenylusing corresponding acids, acid derivatives or halogenated compoundscontaining a group P, such as, for example, (meth)acryloyl chloride or(meth)acrylic acid, in the presence of a dehydrating reagent, such as,for example, DCC (dicyclohexylcarbodiimide).

The preparation of the LC media which can be used in accordance with theinvention is carried out in a manner conventional per se, for example bymixing one or more of the above-mentioned compounds with one or morepolymerisable compounds as defined above, and optionally with furtherliquid-crystalline compounds and/or additives. In general, the desiredamount of the components used in smaller amount is dissolved in thecomponents making up the principal constituent, advantageously atelevated temperature. It is also possible to mix solutions of thecomponents in an organic solvent, for example in acetone, chloroform ormethanol, and to remove the solvent again, for example by distillation,after thorough mixing. The invention furthermore relates to the processfor the preparation of the LC media according to the invention.

It goes without saying to the person skilled in the art that the LCmedia according to the Invention may also comprise compounds in which,for example, H, N, O, Cl or F have been replaced by the correspondingisotopes.

The structure of the LC displays according to the invention correspondsto the usual geometry for PSA displays, as described in the prior artcited at the outset. Geometries without protrusions are preferred, inparticular those in which, in addition, the electrode on thecoloured-filter side is unstructured and only the electrode on the TFTside has slits. Particularly suitable and preferred electrode structuresfor PS-VA displays are described, for example, in US 2006/0066793 A1.

The LC mixtures and LC media according to the invention are in principlesuitable for any type of PS or PSA display, in particular those based onLC media of negative dielectric anisotropy, particularly preferably forPSA-VA, PSA-IPS or PS-FFS displays. However, the person skilled in theart will also be able, without inventive step, to employ suitable LCmixtures and LC media according to the Invention in other displays ofthe PS or PSA type, for example in PS-TN or PS-OCB displays, whichdiffer from the above-mentioned displays, for example, through theirbasic structure or through the nature, arrangement or structure of theindividual components used, such as, for example, the substrates,alignment layers, electrodes, addressing elements, backlighting,polarisers, coloured filters, compensation films optionally present,etc.

The following examples explain the present invention without restrictingit. However, they show the person skilled in the art preferred mixtureconcepts with compounds preferably to be employed and the respectiveconcentrations thereof and combinations thereof with one another. Inaddition, the examples illustrate the properties and propertycombinations that are accessible.

The following abbreviations are used:

(m, m, z: in each case, independently of one another, 1, 2, 3, 4, 5 or6)

TABLE A

In a preferred embodiment of the present invention, the LC mediaaccording to the invention comprise one or more compounds selected fromthe group consisting of compounds from Table A.

TABLE B

Table B shows possible chiral dopants which can be added to the LC mediaaccording to the invention.

The LC media preferably comprise 0 to 10%, in particular 0.01 to 5% andparticularly preferably 0.1 to 3%, of dopants. The LC media preferablycomprise one or more dopants selected from the group consisting ofcompounds from Table B.

TABLE C

Table C shows possible stabilisers which can be added to the LC mediaaccording to the invention.

(n here denotes an integer from 1 to 12)

The LC media preferably comprise 0 to 10%, in particular 1 ppm to 5% andparticularly preferably 1 ppm to 1%, of stabilisers. The LC mediapreferably comprise one or more stabilisers selected from the groupconsisting of compounds from Table C.

TABLE D

RM-1

RM-2

RM-3

RM-4

RM-5

RM-6

RM-7

RM-8

RM-9

RM-10

RM-11

RM-12

RM-13

RM-14

RM-15

RM-16

RM-17

RM-18

RM-19

RM-20

RM-21

RM-22

RM-23

RM-24

RM-25

RM-26

RM-27

RM-28

RM-29

RM-30

Table D shows illustrative compounds which can be used in the LC mediain accordance with the present invention, preferably as reactivemesogenic compounds.

In a preferred embodiment of the present invention, the mesogenic mediacomprise one or more compounds selected from the group of the compoundsfrom Table D.

In addition, the following abbreviations and symbols are used:

-   V₀ threshold voltage, capacitive [V] at 20° C.,-   n_(e) extraordinary refractive index at 20° C. and 589 nm,-   n_(o) ordinary refractive index at 20° C. and 589 nm,-   Δn optical anisotropy at 20° C. and 589 nm,-   ∈_(⊥) dielectric susceptibility perpendicular to the director at    20° C. and 1 kHz,-   ∈_(∥) dielectric susceptibility parallel to the director at 20° C.    and 1 kHz,-   Δ∈ dielectric anisotropy at 20° C. and 1 kHz,-   cl.p., T(N,I) clearing point [° C.],-   γ₁ rotational viscosity at 20° C. [mPa·s],-   K₁ elastic constant, “splay” deformation at 20° C. [pN],-   K₂ elastic constant, “twist” deformation at 20° C. [pN],-   K₃ elastic constant, “bend” deformation at 20° C. [pN],-   LTS low-temperature stability (phase), determined in test cells,-   HR₂₀ voltage holding ratio at 20° C. [%], and-   HR₁₀₀ voltage holding ratio at 100° C. [%].

Unless explicitly noted otherwise, all concentrations and % values (withthe exception of the values for HR, contrast and transmission) in thepresent application are indicated in percent by weight and relate to thecorresponding mixture as a whole comprising all solid orliquid-crystalline components, without solvent.

Unless explicitly noted otherwise, all temperature values indicated inthe present application, such as, for example, the melting point T(C,N),the transition from the smectic (S) to the nematic (N) phase T(S,N) andthe clearing point T(N,I), are indicated in degrees Celsius (° C.). m.p.denotes melting point, cl.p.=clearing point. Furthermore, C=crystallinestate, N=nematic phase, S=smectic phase and I=isotropic phase. The databetween these symbols represent the transition temperatures.

All physical properties are and have been determined in accordance with“Merck Liquid Crystals, Physical Properties of Liquid Crystals”, StatusNovember 1997, Merck KGaA, Germany, and apply for a temperature of 20°C., and Δn is determined at 589 nm and Δ∈ at 1 kHz, unless explicitlyindicated otherwise in each case.

The term “threshold voltage” for the present invention relates to thecapacitive threshold (V₀), also called the Freedericks threshold, unlessexplicitly indicated otherwise. In the examples, as generally usual, theoptical threshold for 10% relative contrast (V₁₀) may also be indicated.

The display used for measurement of the capacitive threshold voltageconsists of two plane-parallel glass outer plates at a separation of 20μm, each of which has, on the inside, an electrode layer and an unrubbedpolyimide alignment layer on top, which effect a homeotropic edgealignment of the liquid-crystal molecules.

The display or test cell used for measurement of the tilt anglesconsists of two plane-parallel glass outer plates at a separation of 4μm, each of which has, on the inside, an electrode layer and a polyimidealignment layer on top, where the two polyimide layers are rubbedantiparallel to one another and effect a homeotropic edge alignment ofthe liquid-crystal molecules.

The polymerisable compounds are polymerised in the display or test cellby irradiation with UVA light for a pre-specified time, with a voltagesimultaneously being applied to the display (usually 10 V to 30 Valternating current, 1 kHz). In the examples, unless indicatedotherwise, a 28 mW/cm² mercury vapour lamp is used, and the intensity ismeasured using a standard UV meter (Ushio UNI meter) fitted with a 365nm band-pass filter.

The tilt angle is determined by rotational crystal experiment(Autronic-Melchers TBA-105). A low value (i.e. a large deviation fromthe 90° angle) corresponds to a large tilt here.

The VHR value is measured as follows: 0.3% of a polymerisable monomericcompound is added to the LC host mixture, and the resultant mixture isintroduced into TN-VHR test cells (rubbed at 90°, TN-polyimide alignmentlayer, layer thickness d≈4 μm). The HR value is determined after 5 minat 100° C. before and after UV exposure for 2 h (sun test) at 1 V, 60Hz, 64 μs pulse (measuring instrument: Autronic-Melchers VHRM-105).

EXAMPLE 1

The nematic LC mixture N1 according to the invention is formulated asfollows, comprising 4% of a compound of the formula I (CPGP-4-3):

CY-3-O2 19.00% cl. p. +78.0 CY-5-O2 2.00% Δn 0.0949 CCY-3-O2 11.00% Δε−3.3 CCY-3-O3 10.00% ε_(∥) 3.5 CCY-4-O2 10.00% K₃/K₁ 1.07 CPY-3-O2 6.00%γ₁ 131 CCH-25 9.00% V₀ 2.17 CCH-34 9.00% BCH-32 6.00% PCH-32 14.00%CPGP-4-3 4.00%

EXAMPLE 2

The nematic LC mixture N2 according to the invention is formulated asfollows, comprising 5% of a compound of the formula I (CPYP-3-2):

CY-3-O2 22.00% cl. p. +80.0 CY-5-O2 2.00% Δn 0.0960 CCY-3-O2 8.00% Δε−3.2 CCY-4-O2 4.00% ε_(∥) 3.5 CPY-2-O2 6.00% K₃/K₁ 1.05 CPY-3-O2 10.00%γ₁ 120 CCH-23 22.00% V₀ 2.26 CCH-34 6.00% BCH-32 4.00% CCH-501 6.00%CCP-3-3 5.00% CPYP-3-2 5.00%

EXAMPLE 3

The nematic LC mixture N3 according to the invention is formulated asfollows, comprising 7% of compounds of the formula I (CCOC-3-3,CCOC-4-3, CBC-33F):

CY-3-O4 24.00% cl. p. +76.1 CCY-3-O2 6.00% Δn 0.0945 CCY-3-O3 3.00% Δε−2.8 CCY-2-1 10.00% ε_(∥) 3.5 CCY-3-1 10.00% K₃/K₁ 0.95 PYP-2-3 10.50%γ₁ 138 PYP-2-4 3.00% V₀ 2.25 CCH-34 14.50% CCH-503 7.00% CCH-501 5.00%CCOC-3-3 2.00% CCOC-4-3 3.00% CBC-33F 2.00%

EXAMPLE 4

The nematic LC mixture N4 according to the invention is formulated asfollows, comprising 4% of compounds of the formula I (CCOC-3-3,CCOC-4-3):

CY-3-O2 20.00% cl. p. +76.0 CY-5-O2 9.00% Δn 0.0956 CCY-3-O3 9.00% Δε−3.2 CCY-4-O2 5.00% ε_(∥) 3.5 CPY-3-O2 7.00% K₃/K₁ 1.04 PYP-2-3 3.00% γ₁132 PYP-2-4 5.00% V₀ 2.24 CCP-31 5.00% CCP-33 5.00% CCH-34 10.00% CCH-2510.00% PCH-302 8.00% CCOC-3-3 2.00% CCOC-4-3 2.00%

COMPARATIVE EXAMPLE 1

The nematic LC mixture C1 is formulated as follows:

CY-3-O4 14.00% cl. p. +70.0 CY-5-O4 13.00% Δn 0.0825 CCY-3-O2 8.00% Δε−3.5 CCY-5-O2 8.00% ε_(∥) 3.5 CCY-21 9.00% K₃/K₁ 1.00 CCY-31 9.00% γ₁141 CPY-2-O2 8.00% V₀ 2.06 CCH-501 9.00% CCH-35 14.00% PCH-53 8.00%

EXAMPLE 5

In each case, 0.3% of RM1 (biphenyl 4,4′-dimethacrylate) is added to LCmixtures N1-N4 according to the invention and to comparative mixture Cl:

The resultant LC media are each introduced into VA e/o test cells asdescribed above. With application of a voltage of 24 V (alternatingcurrent), the cells are irradiated with UV light (365 nm) having anintensity of 50 mW/cm² for various periods, causing polymerisation ofthe RM.

In order to determine the polymerisation rate, the residual content ofunpolymerised RM1 (in % by weight) in the test cells after variousexposure times is measured using the HPLC method. To this end, eachmixture is polymerised in the test cell under the conditions indicated.The mixture is then rinsed out of the test cell using MEK (methyl ethylketone) and measured. The results are summarised in Table 1.

TABLE 1 RM content [%] Exposure time [s] LC medium 0 120 240 360 N1 +RM1 0.3000 0.2185 0.1850 0.1130 N2 + RM1 0.3000 0.1810 0.1170 0.0850N3 + RM1 0.3000 0.1900 0.1130 0.0820 N4 + RM1 0.3000 0.1655 0.11000.0775 C1 + RM1 0,3000 0.2590 0.2005 0.1635

As can be seen from Table 1, only a little unpolymerlsed RM1 is stillpresent in the cell after only a short time in the case of LC mixturesN1-N4 according to the invention, whereas significantly moreunpolymerised RM1 is still present after the respective same exposuretime in the case of comparative mixture C1. A significantly higherpolymerisation rate of RM1 can be concluded therefrom in LC mixturesN1-N4 according to the invention.

Thus, for example, LC medium N1+RM1 according to the invention has a 30%lower RM residual content than comparative medium C1+RM1 after anexposure time of 6 minutes. In the case of LC media N2+RM1, N3+RM1 andN4+RM1 according to the invention, it was even possible for the RMresidual content to be halved compared with comparative medium C1+RM1.

EXAMPLE 6

The LC media described in Example 5 comprising 0.3% of RM1 in LCmixtures N1-N4 or C1 are introduced into VA e/o test cells as describedabove. With application of a voltage of 24 V (alternating current), thecells are irradiated with UV light having a wavelength of 365 nm and anintensity of 50 mW/cm² for various periods, causing polymerisation ofthe RM.

For each test cell, the pretilt angle is determined as indicated above.The pretilt angle achieved in each case for the various exposure timesis summarised in Table 2.

TABLE 2 LC medium Exposure time [s] Tilt [°] N1 + RM1 0 89.1 30 88.1 8082.3 120 76.0 240 71.5 380 67.0 N2 + RM1 0 88.9 30 87.6 60 81.8 120 74.9240 69.9 360 68.5 N3 + RM1 0 89.3 30 87.4 80 80.1 120 74.3 240 71.0 36069.9 N4 + RM1 0 89.0 30 85.7 60 81.3 120 72.2 240 71.8 360 69.5 C1 + RM10 89.5 30 88.8 60 87.4 120 82.7 240 75.6 360 74.1

As can be seen from Table 2, a lower pretilt angle can be achieved withthe LC media according to the invention comprising an LC mixture N1, N2,N3 or N4 according to the invention than with the LC medium comprisingcomparative mixture C1. Table 2 also shows that comparable pretiltangles can already be achieved after significantly shorter exposure timewith LC mixtures N1-N4 according to the invention than with the LCmedium comprising comparative mixture C1.

Thus, for example, comparative medium C1+RM1 exhibits a tilt angle of82.7° after an exposure time of 120 s. By contrast, a similar tilt angleof 82.3° is achieved after only 60 s in the case of LC medium N1+RM1according to the invention, i.e. it was possible to halve the exposuretime compared with the comparative medium.

After an exposure time of 360 s, a tilt angle of 74.1 is achieved in thecase of comparative medium C1+RM1. By contrast, comparable values areachieved after only 120 s, i.e. a third of the time, in the case of LCmedia N2+RM1, N3+RM1 and N4+RM1 according to the invention.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely Illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

The entire disclosure[s] of all applications, patents and publications,cited herein and of corresponding German application No. DE102009018625.5, filed Apr. 23, 2009 are incorporated by referenceherein.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A polymer stabilized (PS) liquid-crystal or polymer sustainedalignment (PSA) liquid crystal display, comprising a liquid-crystalmixture comprising one or more compounds of formula I

in which R¹ and R² each, independently of one another, denote alkylhaving 1 to 12 C atoms, in which one or two non-adjacent CH₂ groups areeach optionally replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such away that O atoms are not linked directly to one another, A1, A2, A³, A⁴each, independently of one another, denote

one, two or three of the radicals A¹, A², A³ and A⁴ may also denote

L¹ and L² each, independently of one another, denote H, F, Cl, OCF₃,CF₃, CH₂F, or CHF₂, Z¹ and Z² each denote a single bond, Z³ denotes—COO—, —OCO—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —SCH₂—, —CH₂S—, —CH₂CH₂—,—C₂F₄—, —CH₂—CF₂—, —CF₂CH₂—, —(CH₂)_(z)—, —CH═CH—, —CF═CF—, —CH═CF—,—CF═CH—, —C≡C—, —CH═CHCH₂O—, or a single bond, z denotes 3, 4, 5 or 6,and m denotes
 1. 2. A display according to claim 1, wherein thecompounds of formula I are selected from the following formulae:

in which alkyl and alkyl* each, independently of one another, denote astraight-chain alkyl radical having 1-12 C atoms, (O) denotes an oxygenatom or a single bond, (CH═CH) denotes an ethenylene group or a singlebond, and L denotes H or F.
 3. A display according to claim 1, whereinthe liquid-crystal mixture further comprises, in addition to said one ormore compounds of formula I, one or more additional compounds of formulaCY and/or PY and/or LY:

in which a denotes 1 or 2, b denotes 0 or 1, f denotes 0 or 1,

denotes

denotes

R¹ and R² each, independently of one another, denote alkyl having 1 to12 C atoms, in which one or two non-adjacent CH₂ groups may be replacedby —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that O atoms are notlinked directly to one another, Z^(x) and Z^(y) each, independently ofone another, denote —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,—COO—, —OCO—, —C₂F₄—, —CF═CF—, —CH═CHCH₂O—, or a single bond, and L¹⁻⁴each, independently of one another, denote F, Cl, OCF₃, CF₃, CH₃, CH₂F,or CHF₂.
 4. A display according to claim 1, wherein the LC mixturefurther comprises one or more compounds of formula ZK:

in which

denotes

denotes

R³ and R⁴ each, independently of one another, denote alkyl having 1 to12 C atoms, in which one or two non-adjacent CH₂ groups may be replacedby —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that O atoms are notlinked directly to one another, and Z^(y) denotes —CH₂CH₂—, —CH═CH—,—CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —COO—, —OCO—, —C₂F₄—, —CF═CF—,—CH═CHCH₂O— or a single bond.
 5. A display according to claim 1, whereinthe LC mixture further comprises one or more compounds of formula DK:

in which R⁵ and R⁶ each, independently of one another, denote alkylhaving 1 to 12 C atoms, in which one or two non-adjacent CH₂ groups maybe replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that Oatoms are not linked directly to one another,

denote

denotes


6. A display according to claim 1, wherein the LC mixture furthercomprises one or more compounds of formula T:

in which R⁵ and R⁶ each, independently of one another, denote alkylhaving 1 to 12 C atoms, in which one or two non-adjacent CH₂ groups maybe replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that Oatoms are not linked directly to one another, and

each, independently of one another, denote

in which L⁵ denotes F or Cl, and L⁶ denotes F, Cl, OCF₃, CF₃, CH₃, CH₂For CHF₂.
 7. A display according to claim 1, wherein the LC mixturecomprises 1 to 25% of one or more compounds of formula I.
 8. A displayaccording to claim 3, wherein the LC mixture comprises one or morecompounds selected from formula CY in which a=1, formula PY in which b=0and formula LY in which f=0, in a total concentration of 1 to 60%.
 9. Adisplay according to claim 3, wherein the LC mixture comprises one ormore compounds selected from formula CY in which a=2 and formula PY inwhich b=1, in a total concentration of 1 to 60%.
 10. A display accordingto claim 1, wherein the LC mixture comprises one or more compoundsselected from formulae ZK1, ZK2, ZK5, ZK6, DK1, DK2, DK4, DK5, B1 andT1, in a total concentration of 1 to 60%

in which alkyl and alkyl* each, independently of one another, denote astraight-chain alkyl radical having 1-6 C atoms, R denotes astraight-chain alkyl or alkoxy radical having 1-7 C atoms, (O) denotesan oxygen atom or a single bond, and m denotes an integer of 1 to
 6. 11.A display according to claim 3, wherein the LC mixture comprises, in atotal concentration of 1 to 50%, one or more compounds selected fromformula CY in which a=2 and R¹, R² denote an alkyl or alkenyl group, andformula T

in which R⁵ and R⁶ each, independently of one another, denote alkylhaving 1 to 12 C atoms, in which one or two non-adjacent CH₂ groups maybe replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that Oatoms are not linked directly to one another, and

each, independently of one another, denote

in which L⁵ denotes F or Cl, and L⁶ denotes F, Cl, OCF₃, CF₃, CH₃, CH₂For CHF₂.
 12. A liquid-crystal medium comprising: a polymerizablecomponent A) comprising one or more polymerizable compounds, or apolymer obtainable by polymerization of a polymerizable component A)comprising one or more polymerizable compounds, and a liquid-crystallinecomponent B) comprising a liquid-crystal (LC) mixture comprising one ormore compounds of formula I

in which R¹ and R² each, independently of one another, denote alkylhaving 1 to 12 C atoms, in which one or two non-adjacent CH₂ groups maybe replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that Oatoms are not linked directly to one another, A¹, A², A³, A⁴ each,independently of one another, denote

one, two or three of the radicals A¹, A², A³ and A⁴ also denote

L¹ and L² each, independently of one another, denote H, F, Cl, OCF₃,CF₃, CH₂F, or CHF₂, Z¹, Z², Z³ each, independently of one another,denote —COO—, —OCO—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —SCH₂—, —CH₂S—,—CH₂CH₂—, —C₂F₄—, —CH₂—CF₂—, —CF₂CH₂—, —(CH₂)_(z)—, —CH═CH—, —CF═CF—,—CH═CF—, —CF═CH—, —C≡C—, —CH═CHCH₂O—, or a single bond, where, in thecase where m=0, Z¹ and Z² do not simultaneously denote a single bond, zdenotes 3, 4, 5 or 6, and m denotes 0 or 1, wherein said medium does notcontain chiral compounds.
 13. A liquid-crystal medium according to claim12, wherein said medium comprises a polymerizable component A)comprising one or more polymerizable compounds, and a liquid-crystallinecomponent B) comprising a liquid-crystal (LC) mixture comprising one ormore compounds of formula I.
 14. A liquid-crystal medium according toclaim 12, wherein said medium comprises a polymer obtainable bypolymerization of a polymerizable component A) comprising one or morepolymerizable compounds, and a liquid-crystalline component B)comprising a liquid-crystal (LC) mixture comprising one or morecompounds of formula I.
 15. A method for generating a tilt angle in aliquid-crystal medium in a polymer stabilized (PS) or polymer sustainedalignment (PSA) display by in-situ polymerization of polymerizablecompound(s) in the display, wherein the liquid-crystal medium isaccording to claim 12, said method comprising applying an electric ormagnetic field to said medium.
 16. A liquid-crystal display of thepolymer stabilized (PS) type or of the polymer sustained alignment (PSA)type containing an LC medium according to claim
 12. 17. A liquid-crystaldisplay according to claim 16, wherein said display is a PSA-VA, PS-IPSor PS-FFS display.
 18. A liquid-crystal display containing an LC cellcontaining two substrates, where at least one substrate is transparentto light and at least one substrate has an electrode layer, and a layer,located between the substrates, of a liquid-crystal medium comprising apolymerized component and a low-molecular-weight component, where thepolymerized component is obtainable by polymerization of one or morepolymerizable compounds in the LC medium between the substrates of theliquid-crystal cell with application of an electrical voltage, and wherethe low-molecular-weight component is a liquid-crystal mixturecomprising one or more compounds of formula I

in which R¹ and R² each, independently of one another, denote alkylhaving 1 to 12 C atoms, in which one or two non-adjacent CH₂ groups maybe replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that Oatoms are not linked directly to one another, A¹, A², A³, A⁴ each,independently of one another, denote

one, two or three of the radicals A¹, A², A³ and A⁴ may also denote

L¹ and L² each, independently of one another, denote H, F, Cl, OCF₃,CF₃, CH₂F, or CHF₂, Z¹, Z², Z³ each, independently of one another,denote —COO—, —OCO—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —SCH₂—, —CH₂S—,—CH₂CH₂—, —C₂F₄—, —CH₂—CF₂—, —CF₂CH₂—, —(CH₂)_(z)—, —CH═CH—, —CF═CF—,—CH═CF—, —CF═CH—, —C≡C—, —CH═CHCH₂O—, or a single bond, where, in thecase where m=0, Z¹ and Z² do not simultaneously denote a single bond, zdenotes 3, 4, 5 or 6, and m denotes 0 or
 1. 19. A process for theproduction of a liquid-crystal display according to claim 18, comprisingmixing the liquid-crystal mixture comprising one or more compounds offormula I with one or more polymerizable compounds and optionally withfurther liquid-crystalline compounds and/or additives, introducing theresultant mixture into a liquid-crystal cell, and polymerising thepolymerizable compound(s) with application of an electrical voltage. 20.A display according to claim 1, wherein the liquid-crystal mixturefurther comprises a polymerizable component which comprises one or morepolymerizable compounds of formula I*R^(a)—B¹—(Z^(b)—B²)_(m)—R^(b)  I* in which R^(a) and R^(b) each,independently of one another, denote P, P-Sp-, H, halogen, SF₅, NO₂, acarbon group or hydrocarbon group, where at least one of the radicalsR^(a) and R^(b) denotes or contains a group P or P-Sp-, P on eachoccurrence, identically or differently, denotes a polymerizable group,Sp on each occurrence, identically or differently, denotes a spacergroup or a single bond, B¹ and B² each, independently of one another,denote an aromatic, heteroaromatic, alicyclic or heterocyclic group,which may also contain fused rings, and which may also be mono- orpolysubstituted by L, L denotes P-Sp-, H, OH, CH₂OH, halogen, SF₅, NO₂,a carbon group or hydrocarbon group, Z^(b) on each occurrence,identically or differently, denotes —O—, —S—, —CO—, —CO—O—, —OCO—,—O—CO—O—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—,—SCF₂—, —(CH₂)_(n1)—, —CF₂CH₂—, —CH₂CF₂—, —(CF₂)_(n1)—, —CH═CH—,—CF═CF—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or a single bond, R⁰and R⁰⁰ each, independently of one another, denote H or alkyl having 1to 12 C atoms, m denotes 0, 1, 2, 3 or 4, and n1 denotes 1, 2, 3 or 4.21. A display according to claim 20, wherein the concentration of thepolymerizable component is ≦5% and ≧0.01%.
 22. A liquid-crystal mediumaccording to claim 12, wherein the polymerizable component comprises oneor more polymerizable compounds of formula I*R^(a)—B¹—(Z^(b)—B²)_(m)—R^(b)  I* in which R^(a) and R^(b) each,independently of one another, denote P, P-Sp-, H, halogen, SF₅, NO₂, acarbon group or hydrocarbon group, where at least one of the radicalsR^(a) and R^(b) denotes or contains a group P or P-Sp-, P on eachoccurrence, identically or differently, denotes a polymerizable group,Sp on each occurrence, identically or differently, denotes a spacergroup or a single bond, B¹ and B² each, independently of one another,denote an aromatic, heteroaromatic, alicyclic or heterocyclic group,which may also contain fused rings, and which may also be mono- orpolysubstituted by L, L denotes P-Sp-, H, OH, CH₂OH, halogen, SF₅, NO₂,a carbon group or hydrocarbon group, Z^(b) on each occurrence,identically or differently, denotes —O—, —S—, —CO—, —CO—O—, —OCO—,—O—CO—O—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—,—SCF₂—, —(CH₂)_(n1)—, —CF₂CH₂—, —CH₂CF₂—, —(CF₂)_(n1)—, —CH═CH—,—CF═CF—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or a single bond, R⁰and R⁰⁰ each, independently of one another, denote H or alkyl having 1to 12 C atoms, m denotes 0, 1, 2, 3 or 4, and n1 denotes 1, 2, 3 or 4.23. An LC medium according to claim 12, wherein the concentration of thepolymerizable component is ≦5% and ≧0.01%.
 24. A display according toclaim 1, wherein R¹ and R² each, independently of one another, denotealkyl or alkoxy having 1 to 6 C atoms.
 25. A liquid-crystal displaycontaining a liquid-crystal medium according to claim
 13. 26. Theliquid-crystal display according to claim 25, wherein said display is ofthe polymer stabilized (PS) type or of the polymer sustained alignment(PSA) type.
 27. A liquid-crystal display containing a liquid-crystalmedium according to claim
 14. 28. The liquid-crystal display accordingto claim 27, wherein said display is of the polymer stabilized (PS) typeor of the polymer sustained alignment (PSA) type.
 29. A displayaccording to claim 1, wherein L¹ and L² are each selected from H, F orCl.
 30. A liquid-crystal medium according to claim 1, wherein Z³ is—CH₂O— or a single bond.
 31. A display according to claim 1, wherein A¹,A², A³, A⁴ are each, independently of one another, 1,4-cyclohexylene,1,4-cyclohexenylene, tetrahydropyran-1,4,-diyl, ortetrahydropyran-1,4,-diyl.
 32. A display according to claim 1, whereinR¹ and R² are each, independently of one another, straight-chain alkylhaving 1 to 6 C atoms, straight-chain alkoxy having 1 to 6 C atoms, orstraight-chain alkenyl having 2 to 7 C atoms.
 33. A display according toclaim 1, wherein A¹, A², A³, A⁴ are each, independently of one another,


34. A liquid-crystal medium according to claim 12, wherein L¹ and L² areeach selected from H, F or Cl.
 35. A liquid-crystal medium according toclaim 12, wherein Z³ is —CH₂O— or a single bond.
 36. A liquid-crystalmedium according to claim 12, wherein A¹, A², A³, A⁴ are each,independently of one another, 1,4-cyclohexylene, 1,4-cyclohexenylene,tetrahydropyran-1,4,-diyl, or tetrahydropyran-1,4,-diyl.
 37. Aliquid-crystal medium according to claim 12, wherein R¹ and R² are each,independently of one another, straight-chain alkyl having 1 to 6 Catoms, straight-chain alkoxy having 1 to 6 C atoms, or straight-chainalkenyl having 2 to 7 C atoms.
 38. A liquid-crystal medium according toclaim 12, wherein A¹, A², A³, A⁴ are each, independently of one another,


39. A liquid-crystal medium according to claim 22, wherein R^(a) andR^(b) each, independently of one another, denote P, P-Sp-, H, F, Cl, Br,I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN, SF₅ or straight-chain or branchedalkyl having 1 to 25 C atoms, in which, in addition, one or morenon-adjacent CH₂ groups are each optionally replaced, independently ofone another, by —C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰⁰)—, —O—, —S—, —CO—, —CO—O—,—O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsmay be replaced by F, Cl, Br, I, CN, P or P-Sp-, where at least one ofthe radicals R^(a) and R^(b) denotes or contains a group P or P-Sp-,where, if B¹ and/or B² contain a saturated C atom, R^(a) and/or R^(b)may also denote a radical which is spiro-linked to this saturated Catom, B¹ and B² each, independently of one another, denote1,4-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl,phenanthrene-2,7-diyl, anthracene-2,7-diyl, fluorene-2,7-diyl,coumarine, flavone, where, in addition, one or more CH groups in thesegroups m are each optionally replaced by N, cyclohexane-1,4-diyl, inwhich, in addition, one or more non-adjacent CH₂ groups are eachoptionally replaced by O and/or S, 1,4-cyclohexenylene,bicycle[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl, piperidine-1,4-diyl,decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl,indane-2,5-diyl or octahydro-4,7-methanoindane-2,5-diyl, where all thesegroups are unsubstituted or mono- or polysubstituted by L, and L denotesP, P-Sp-, OH, CH₂OH, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN,—C(═O)N(R^(x))₂, —C(═O)Y¹, —C(═O)R^(x), —N(R^(x))₂, optionallysubstituted silyl, optionally substituted aryl having 6 to 20 C atoms,or straight-chain or branched alkyl, alkoxy, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 Catoms, in which, in addition, one or more H atoms are each optionallyreplaced by F, Cl, P or P-Sp-.
 40. A liquid-crystal medium according toclaim 22, wherein the compounds of formula I* are selected from formulaeM1-M28:

wherein: P¹ and P² each, independently of one another, denote apolymerizable group, Sp¹ and Sp² each, independently of one another,denote a single bond or a spacer group, and where one or more of theradicals P¹-Sp¹- and P²-Sp²- may denote R^(aa), with the proviso that atleast one of the radicals P¹-Sp¹- and P²-Sp²- present does not denoteR^(aa), R^(aa) denotes H, F, Cl, CN or straight-chain or branched alkylhaving 1 to 25 C atoms, in which, in addition, one or more non-adjacentCH₂ groups are each optionally replaced, independently of one another,by C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—,—O—CO—O— in such a way that O and/or S atoms are not linked directly toone another, and in which, in addition, one or more H atoms are eachoptionally replaced by F, Cl, CN or P¹-Sp¹-, R⁰, R⁰⁰ each, independentlyof one another and identically or differently on each occurrence, denoteH or alkyl having 1 to 12 C atoms, R^(y) and R^(z) each, independentlyof one another, denote H, F, CH₃ or CF₃, Z¹ denotes —O—, —CO—,—C(R^(y)R^(z))—, or —CF₂CF₂—, Z² and Z³ each, independently of oneanother, denote —CO—O—, —O—CO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or—(CH₂)_(n)—, where n is 2, 3 or 4, L on each occurrence, identically ordifferently, denotes F, Cl, CN or straight-chain or branched, optionallymono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 Catoms, L′ and L″ each, independently of one another, denote H, F or Cl,r denotes 0, 1, 2, 3 or 4, s denotes 0, 1, 2 or 3, t denotes 0, 1 or 2,and x denotes 0 or
 1. 41. A display according to claim 16, wherein thepolymerizable component comprises one or more polymerizable compounds offormula I*R^(a)—B¹—(Z^(b)—B²)_(m)—R^(b)  I* in which R^(a) and R^(b) each,independently of one another, denote P, P-Sp-, H, halogen, SF₅, NO₂, acarbon group or hydrocarbon group, where at least one of the radicalsR^(a) and R^(b) denotes or contains a group P or P-Sp-, P on eachoccurrence, identically or differently, denotes a polymerizable group,Sp on each occurrence, identically or differently, denotes a spacergroup or a single bond, B¹ and B² each, independently of one another,denote an aromatic, heteroaromatic, alicyclic or heterocyclic group,which may also contain fused rings, and which may also be mono- orpolysubstituted by L, L denotes P-Sp-, H, OH, CH₂OH, halogen, SF₅, NO₂,a carbon group or hydrocarbon group, Z^(b) on each occurrence,identically or differently, denotes —O—, —S—, —CO—, —CO—O—, —OCO—,—O—CO—O—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—,—SCF₂—, —(CH₂)_(n1)—, —CF₂CH₂—, —CH₂CF₂—, —(CF₂)_(n1)—, —CH═CH—,—CF═CF—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH—, CR⁰R⁰⁰ or a single bond, R⁰and R⁰⁰ each, independently of one another, denote H or alkyl having 1to 12 C atoms, m denotes 0, 1, 2, 3 or 4, and n1 denotes 1, 2, 3 or 4.42. A display according to claim 41, wherein R^(a) and R^(b) each,independently of one another, denote P, P-Sp-, H, F, Cl, Br, I, —CN,—NO₂, —NCO, —NCS, —OCN, —SCN, SF₅ or straight-chain or branched alkylhaving 1 to 25 C atoms, in which, in addition, one or more non-adjacentCH₂ groups are each optionally replaced, independently of one another,by —C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—,—O—CO—O— in such a way that O and/or S atoms are not linked directly toone another, and in which, in addition, one or more H atoms may bereplaced by F, Cl, Br, I, CN, P or P-Sp-, where at least one of theradicals R^(a) and R^(b) denotes or contains a group P or P-Sp-, where,if B¹ and/or B² contain a saturated C atom, R^(a) and/or R^(b) may alsodenote a radical which is spiro-linked to this saturated C atom, B¹ andB² each, independently of one another, denote 1,4-phenylene,naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-2,7-diyl,anthracene-2,7-diyl, fluorene-2,7-diyl, coumarine, flavone, where, inaddition, one or more CH groups in these groups m are each optionallyreplaced by N, cyclohexane-1,4-diyl, in which, in addition, one or morenon-adjacent CH₂ groups are each optionally replaced by O and/or S,1,4-cyclohexenylene, bicycle[1.1.1]pentane-1,3-diyl,bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl,piperidine-1,4-diyl, decahydronaphthalene-2,6-diyl,1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl oroctahydro-4,7-methanoindane-2,5-diyl, where all these groups areunsubstituted or mono- or polysubstituted by L, and L denotes P, P-Sp-,OH, CH₂OH, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN,—C(═O)N(R^(x))₂, —C(═O)Y¹, —C(═O)R^(x), —N(R^(x))₂, optionallysubstituted silyl, optionally substituted aryl having 6 to 20 C atoms,or straight-chain or branched alkyl, alkoxy, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 Catoms, in which, in addition, one or more H atoms are each optionallyreplaced by F, Cl, P or P-Sp-.
 43. A display according to claim 41,wherein the compounds of formula I* are selected from formulae M1-M28:

wherein: P¹ and P² each, independently of one another, denote apolymerizable group, Sp¹ and Sp² each, independently of one another,denote a single bond or a spacer group, and where one or more of theradicals P¹-Sp¹- and P²-Sp²- may denote R^(aa), with the proviso that atleast one of the radicals P¹-Sp¹- and P²-Sp²- present does not denoteR^(aa), R^(aa) denotes H, F, Cl, CN or straight-chain or branched alkylhaving 1 to 25 C atoms, in which, in addition, one or more non-adjacentCH₂ groups are each optionally replaced, independently of one another,by C(R⁰)═C(R⁰)—, —C≡C—, —N(R⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—,—O—CO—O— in such a way that O and/or S atoms are not linked directly toone another, and in which, in addition, one or more H atoms are eachoptionally replaced by F, Cl, CN or P¹-Sp¹-, R⁰, R⁰⁰ each, independentlyof one another and identically or differently on each occurrence, denoteH or alkyl having 1 to 12 C atoms, R^(y) and R^(z) each, independentlyof one another, denote H, F, CH₃ or CF₃, Z¹ denotes —O—, —CO—,—C(R^(y)R^(z))—, or —CF₂CF₂—, Z² and Z³ each, independently of oneanother, denote —CO—O—, —O—CO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or—(CH₂)_(n)—, where n is 2, 3 or 4, L on each occurrence, identically ordifferently, denotes F, Cl, CN or straight-chain or branched, optionallymono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 Catoms, L′ and L″ each, independently of one another, denote H, F or Cl,r denotes 0, 1, 2, 3 or 4, s denotes 0, 1, 2 or 3, t denotes 0, 1 or 2,and x denotes 0 or 1.